Friendly Proliferation

Introduction

For the past seven decades, the United States has leveraged its nonproliferation policy as a central pillar of alliance management. Under this long-standing arrangement, the United States provides robust extended deterrence in exchange for an explicit commitment from partners to renounce nuclear ambitions. For over 50 years, the Nuclear Non-Proliferation Treaty (NPT) and the International Atomic Energy Agency have formed the backbone of this “Grand Bargain,” ensuring compliance to prevent nuclear proliferation and avoid the diversion of civilian materials for military use.

However, since Donald Trump’s first administration, a reexamination of U.S. foreign policy has resulted in renewed discussions on friendly proliferation—the notion that Washington could permit or assist certain allies in acquiring nuclear capabilities. In 2016, then-candidate Trump characterized the prospect of Japan and South Korea developing their own nuclear capabilities as inevitable and potentially beneficial for both the United States and its allies. These claims were highly debated, particularly since President Trump also voiced concerns about multiplying nuclear weapons, contradicting those seemingly favorable views of proliferation.

Debates about friendly proliferation resumed in 2026 with the second Trump administration. This resurgence was fueled by the fact that several individuals who joined the administration, in particular Elbridge Colby—under secretary of defense for policy at the Pentagon—had mentioned friendly proliferation in their writings when working at think tanks. Although Colby rebutted the concept upon entering his official position, stating that the United States would “strenuously oppose” proliferation (particularly in a European context), the second Trump administration’s approach toward nonproliferation norms has continued to fuel fears among observers both in the United States and abroad.

Simultaneously, domestic debates on indigenous nuclear programs within allied nations, both in Asia and in Europe, have intensified significantly. In Asia, for example, while South Korean conservatives have campaigned on nuclearization for over a decade, President Yoon Suk-yeol’s 2023 comments on the South Korean capacity to build nuclear weapons marked a qualitative shift by bringing the debate to the presidential level. This rhetoric is primarily driven by the threat of a nuclear-armed North Korea, but it has been exacerbated by lingering anxieties over the sustainability of the U.S. security umbrella. Though tempered since the 2023 Washington Declaration, nuclear proliferation remains actively debated in Seoul and Tokyo. Similarly, in Europe, the acute Russian nuclear threat, combined with an evolving U.S. approach to NATO, have generated a sense of urgency to bolster deterrence on the Continent. In Poland, Germany, and the Nordic countries, vocal national debates have emerged in recent years, reflecting an unprecedented crisis of confidence in traditional security arrangements.

This report examines how friendly proliferation is discussed within the U.S. expert community and its potential impact on proliferation risks and U.S. alliances. Relying on 42 interviews with stakeholders based in U.S. think tanks and academia, this study operates on the premise that allied debates are heavily shaped by the shifts occurring within this domestic discourse (see Appendix I for more details on the project methodology).

Many experts included in this study noted that the outlook on supporting friendly proliferation is trending in a more positive direction compared to five or ten years ago. While the majority of the community remains opposed to friendly proliferation, growing curiosity among smaller subsets of experts has turned the concept into an increasingly discussed contingency within the U.S. strategic community. This surging discourse does not imply automatic acceptance by political elites. Instead, the expanding debate highlights the mounting challenges of upholding nonproliferation standards in an increasingly dangerous strategic environment. Ultimately, it reflects a broader reconfiguration of U.S. foreign policy priorities and the shifting dynamics of alliance management in 2026.

The primary objective of this report is to deconstruct the friendly proliferation debate with the aim of fostering a deeper understanding of the issues, both within the U.S. strategic community and between the United States and its allies and partners. The report is organized as follows: (1) a brief history and a terminology of the concept; (2) an analysis of the positions held by U.S. experts; (3) the expert perspectives on the drivers of policy adaptation regarding nonproliferation; and (4) a set of strategic policy recommendations for addressing collectively, among allies and partners, the challenges posed by the friendly proliferation debate.

Explaining Friendly Proliferation: History and Conceptual Contours

Friendly proliferation has transitioned from a relatively fringe discussion to a more mainstream debate within the U.S. strategic community. The overwhelming majority of experts interviewed (40 out of 42) confirm that the concept is frequently discussed in their circles. In the realm of foreign policy theory, what was a marginal concept in 2016 has become an openly discussed option by the U.S. expert community on defense in 2026.

Reflecting this broader discourse, definitions of friendly proliferation vary and crystallize several—sometimes antagonistic—visions of future U.S. national security, particularly regarding its alliance management strategy and the traditional role of the United States as a gatekeeper of the nonproliferation regime.

History of the Concept

The intellectual genealogy of friendly proliferation stretches back to the strategic debates of the mid-twentieth century. During the 1950s, against the backdrop of intense competition between the United States and the Soviet Union, the emergence of independent nuclear powers in the United Kingdom and France forced theorists like Thomas Schelling and Albert Wohlstetter to grapple with the logic of separate centers of decisionmaking—the idea that independent nuclear commands within an alliance increase an adversary’s uncertainty and complicate their risk calculus. During the 1960s and 1970s, the universalist aspirations of the nascent nonproliferation regime were tested by a series of historical cases that redefined Washington’s approach to nonproliferation among allies and partners.

In this context, Henry Kissinger and other policymakers pursued a pragmatic path, prioritizing the stability of critical security partnerships over the prohibitive costs of enforcing nonproliferation. This was most evident in the cases of Israel, where the United States tacitly accepted an opaque nuclear status as the cost of maintaining a key regional partnership, and West Germany, where the United States eventually agreed to share sensitive technologies to avoid alienating a frontline NATO partner. The 1964 Chinese nuclear test triggered a profound dilemma for U.S. policy toward India. In the face of a nuclear China, Washington was forced to weigh the systemic risks of a regional proliferation cascade against the difficulty of providing credible security guarantees that did not entail overextending U.S. commitments.

In the 1980s, Kenneth Waltz created the theoretical backdrop in which pro-proliferation policies became thinkable. In his 1981 The Spread of Nuclear Weapons, Waltz argued proliferation could be stabilizing, claiming that nuclear weapons would compel rational behavior in political leaders. In the policy realm, this theory met with deep skepticism rooted in the prevailing consensus of universal restraint. In addition, the more mainstream view contended that nuclear spread was inherently dangerous because it increased the risk of unauthorized use or of organizational failure. Traditional U.S. nonproliferation policy was thus crafted on the premise that a higher number of nuclear actors statistically heightened the risk of regional escalation. Consequently, proliferation, even among allies, was seen as fundamentally detrimental to U.S. interests and global stability.

Formal theorization of friendly proliferation emerged in the 2010s within the framework of discussions on U.S. strategy in Asia. Building on “willingness-opportunity” models from scholars like Scott Sagan, Alexandre Debs, and Nuno P. Monteiro—which weigh a state’s internal motivations against its external strategic and technical capabilities—academic debates emerged on whether supporting such proliferation could be beneficial or even manageable. The term “friendly proliferation” has long existed in strategic literature, but it became a focal point of contemporary policy debates in the mid-2010s with the debate over redeploying U.S. tactical nuclear weapons in Asia. David Santoro, president and CEO of the Pacific Forum, used the term not to endorse the idea, but rather to argue against its feasibility, contending that Washington could neither effectively manage nor quietly tolerate independent nuclear deterrents in Japan or South Korea. Santoro’s article was met by a counterargument from Elbridge Colby, then codirector of the Marathon Initiative, who argued that strict adherence to nonproliferation should not always be the primary U.S. objective. Instead, Colby suggested, geopolitical stability and the regional balance of power against China must sometimes take precedence over nonproliferation norms.

The debate soon expanded beyond defense expert circles into grand strategy and regional studies. Doug Bandow of the Cato Institute added a retrencher dimension, suggesting that the nuclearization of Asian allies might be a pragmatic way for the United States to reduce the mounting burden on its military. Bandow’s argument aligns with John Mearsheimer’s theory of offshore balancing, which posits that the United States should allow regional partners to determine their own containment efforts—potentially including nuclear ones—to preserve U.S. power. In regional studies, scholars such as Robert Kelly have argued that, specifically for South Korea, going nuclear may be the best remaining solution both to counter the North Korean threat and to address growing domestic anxieties in the south regarding the reliability of the U.S. nuclear umbrella.

Ultimately, these arguments from a minority in favor of friendly proliferation signaled a shift toward prioritizing allied self-reliance in increasingly contested theaters, even if academic theorists and policy practitioners often arrived at these conclusions through different professional lenses.

Conceptual Contours: Definitional Ambiguity and Strategic Contradictions

The data compiled in this study reveal, first, that the term friendly proliferation is particularly ill-defined, with the expert community lacking consensus as to the substantive form of such proliferation.

Despite the unclear specifics, experts highlighted the inherent paradox raised by William Foster in 1965—the U.S. effort to maintain strategic leverage over allies is fundamentally undermined by the very act of proliferation. In other words, once an ally acquires a nuclear deterrent, their newfound strategic autonomy—or potential for direct opposition—effectively dissolves the United States’ ability to influence their future security choices.

Despite this paradox, the definitions provided by experts reveal three distinct models for how such “friendly” proliferation could manifest.

1. The most common model—offered by 32 experts—involves the development of an indigenous arsenal from scratch, including nuclear material, weapons, and delivery systems. Though this remains the most resource intensive and politically risky path for an ally—carrying the threat of diplomatic isolation, sanctions, and being cast out of the international community—it is also the most frequent definition of friendly proliferation, as it resembles historical precedents such as those of the United Kingdom and France.
2. The second-most-given definition (five experts) is nuclear latency, specifically, building on civil nuclear energy programs to hedge for nuclear weapons and used as a new form of deterrence. In this view, friendly proliferation does not require a completed weapon. Instead, it involves moving up the nuclear ladder through dual-use capabilities or civilian programs to a point where an ally remains only months away from a functional device. South Korea is often cited as an example of this strategy.
3. The third model—offered by four experts—supposes a “significant extension” of the existing extended deterrence framework in which allies would be given more nuclear prerogatives. This model departs from current NATO nuclear-sharing arrangements, in which the United States maintains sole custody of warheads, by granting allies a higher degree operational control over, or even facilitating the direct transfer of, tactical nuclear weapons. This understanding of friendly proliferation appealed to some experts because it provides the impression that Washington could satisfy an ally’s security needs while still ensuring alignment with U.S. grand strategy.

This research also revealed that, beyond the three technical conceptualizations outlined above, experts identified an overarching active-passive divide in how Washington might facilitate or respond to friendly proliferation. Specifically,

• An active posture would involve the United States directly aiding or accelerating an ally’s program—much like the secret technical assistance the United States provided to France in the 1970s—to ensure that the resulting arsenal is technically secure and strategically aligned with U.S. interests.
• A passive posture would see the United States adopt a policy of “silent acquiescence.” In this scenario, Washington would neither assist nor strenuously oppose an ally’s pursuit of a nuclear deterrent, effectively accepting a de facto nuclearization as a pragmatic trade-off for reduced military commitments.

Because the very concept of friendly proliferation intrinsically addresses postures of accommodation rather than prevention—suggesting an inherently permissive, nonoppositional approach from Washington—this framework sets aside traditional counter-proliferation leverage, such as threatening to sever alliances if an ally decides to go nuclear. Therefore, while a third path of active U.S. opposition remains a critical strategic reality, it falls outside the scope of this research.

Application of the active-passive framework depends heavily on the typology of the “friendly” actor involved. While the framework primarily concerns formal treaty allies like NATO members, Japan, or South Korea, experts often included other security partners when defining “friends” as a broader category, encompassing non-treaty partners like Taiwan, Israel, Ukraine, or even states in the Middle East, such as the Kingdom of Saudi Arabia and the United Arab Emirates.

This fluidity in who is a “friend,” however, invites significant risk: Experts warn that friendship is a fluctuating qualification that may fail to account for proliferation driven by a defiance of, rather than reliance on, Washington. In other words, a state’s decision to develop nuclear weapons could stem from a fear of U.S. abandonment, leading that ally to distance itself from Washington and pursue autonomous deterrence regardless of U.S. nonproliferation pressure. Several participants went so far as to argue that the term friendly proliferation is dangerous in and of itself because it minimizes subsequent irreversible changes to alliance dynamics and the global order. Many interviewees pointed out that the term is not always used in expert debates, and, in fact, is often avoided because of its perceived negative connotations. These experts noted that expressions such as selective allied proliferation, nuclear participation, or strategic latency frequently serve as synonyms for friendly proliferation in their discussions. This confused terminology reveals fluctuating understandings of what proliferation encompasses and points to increasingly blurred lines between traditional nuclear-sharing strategies and the acceptability of using civil nuclear energy programs as a hedge for nuclear weapons.
 

Mapping Expert Positions: A Resilient Consensus Meets Growing Polarization

An Expanding but Contentious Debate

Because nuclear proliferation is traditionally associated with rogue states, a persistent stigma obscures the debate over friendly proliferation. This has resulted in, for example, the selective historical narrative that frames allied nuclear programs—such as those of France and the United Kingdom—as isolated incidents, not precedents. In practice, the United States has historically utilized a combination of extended deterrence and civil nuclear incentives to prevent advanced allies—such as West Germany, Japan, and Sweden—from transitioning from technical hedging to a full-blown nuclear military program.

Despite this legacy, however, the taboo surrounding friendly proliferation is eroding, giving way to more open discourse and even public advocacy in some academic circles. Many experts included here (19) noted that the outlook on the strategy is now “more positive” or “trending positive” compared to five or ten years ago. While the majority of the community (21 experts) remains opposed to friendly proliferation, growing curiosity among smaller subsets of experts has turned the concept into an increasingly discussed contingency within the U.S. strategic community.

Notably, the increase in discussions on friendly proliferation does not mean that the concept has become mainstream or is widely approved. In fact, this research suggests that opposition to the concept remains the dominant position across much of the political spectrum. The data do, however, reveal significant splits based, first, on political affiliation and, second, on professional background.

First, and perhaps not surprisingly, perceptions of friendly proliferation are polarized along ideological lines. Despite the fact that historically nonproliferation was treated as a rare island of bipartisan consensus, the data collected suggest that this bipartisan consensus is thinning as a result of a polarization of foreign policy trends.

• Opposition to the concept remains the predominant view from the left to the center-right. In this view, limiting the spread of nuclear weapons is seen as both a strategic necessity and a moral imperative. Therefore, it remains in the United States’ national interest to prevent proliferation in order to ensure that Washington retains central control over escalation dynamics. Moreover, supporters of this view see the universality of the NPT as incompatible with a selective approach. This means that, while Washington has historically managed specific proliferation pressures through discreet, case-by-case adjustments, moving to an explicit endorsement of friendly proliferation would undermine the normative consistency that the United States relies upon to discourage adversarial programs. Finally, this group views endorsing allied nuclearization as something that would erode the U.S. position in international fora—UN bodies involved in the NPT cycles in particular—resulting in contested leadership and a loss of the moral high ground required for multilateral diplomacy.
• Conversely, openness to the concept of friendly proliferation is found primarily among conservatives who self-describe as “realists” on foreign policy. These proponents argue that friendly proliferation could be selectively permitted to create a decentralized regional deterrence effect against adversaries, specifically China. In this view, friendly proliferation is a way to reinforce U.S. security interests by reducing the burden on the U.S. military. Participants who identify as “restrainers” (a group that transcends traditional partisan labels) and who consider the reduction of U.S. global commitments an explicit primary objective that outweighs the preservation of nonproliferation norms also made this argument.

Second, it appears that the deeper the expertise individuals have on nuclear proliferation and its specific implications (technical, financial, political), the less prone they are to advocating in favor of friendly proliferation. While official circles and technical nuclear experts remained overwhelmingly negative—citing, among others, deleterious effects on global stability—there was a more pronounced intellectual curiosity among grand strategy and regional experts.

• On the one hand, topical nuclear experts maintained a broad consensus that nonproliferation is a nonnegotiable pillar of S. foreign policy. They emphasized various risks related to proliferation, in particular a heightened risk of accident or miscalculation, the loss of U.S. political and military control in specific contingencies, and the danger of a collapse of the NPT regime. In this regard, the consensus in favor of nonproliferation that prevails at the official level seems to be upheld by the arguments presented by the nuclear expert community.
• On the other hand, grand strategy and regional experts appeared more open to considering friendly proliferation as a means of reinforcing deterrence in regional contingencies in the face of growing Chinese or Russian threats, particularly at a time when U.S. security guarantees are overstretched across theaters. Especially for those who advocate for a “retrenchment” or “prioritization” in U.S. foreign policy, a shift toward friendly proliferation could be driven by the belief that allied nuclearization may be the only viable solution to a resource-constrained U.S. defense posture, either to facilitate unilateral withdrawal from certain theaters or to adapt to a two-peer nuclear threat. Another category of regional experts did not view friendly proliferation positively, but did see it as inevitable in the security logic of allies who perceive a weakening of U.S. extended deterrence commitment.

Interviewees also highlighted a conceptual and professional divide that separates traditional nonproliferation advocates from the minority now contemplating friendly proliferation. This institutional firewall functions as a siloing mechanism: Nonproliferation experts typically operate within a framework of international law and treaty preservation (particularly the NPT), while those open to allied proliferation prioritize regional deterrence and burden-shifting. Consequently, these two camps rarely engage in direct dialogue, instead often operating in parallel rather than in conversation. This lack of interaction forces each side to rely on assumptions about the other’s motivations, preventing a more integrated discussion on the future of U.S. foreign policy.

On one side, defenders of the existing nonproliferation policy argue that the increased frequency of discussions on friendly proliferation creates an illusion of consensus. They contend that this atmosphere dismisses the fact that only a small minority actually advocates for the concept, while ignoring the immense political and military barriers to any formal policy change. On the other hand, advocates of friendly proliferation—or at least advocates of discussing it more openly—often characterize defenders of the status quo as “normative zealots” who lack practical military experience. In their view, nonproliferation advocates prioritize the survival of institutional norms as an end in itself, rather than pursuing more efficient military adaptations to a changing security environment.

Likelihood of Formal Adoption into U.S. Policy

Despite the growing intensity of the debate, the vast majority of experts (30 participants) argue that it is highly unlikely that friendly proliferation will translate into a formal change in official U.S. nonproliferation policy. In explaining their reasoning, respondents emphasized the weight of international commitments and institutional guardrails—for example, congressional oversight and statutory requirements to enforce sanctions—as significant barriers to any such shift. These experts also highlighted the profound uncertainty involved in such a policy move, noting the high risk of it backfiring on global security and U.S. strategic interests.

Notably, many experts did not rule out the possibility of friendly proliferation manifesting in a more passive manner. A significant segment of the sample (7 participants), in fact, viewed a potential pivot toward a strategy of tacit tolerance—or what some termed “silent acquiescence”—as increasingly plausible. An additional minority (5 experts) believed that this could occur either eventually in the long run or under “extreme forcing functions,” such as one involving Taiwan. The experts cited a Taiwan contingency as a decisive geopolitical shock that could expose the limits of U.S. regional power. In the aftermath of such a crisis, these experts suggested, the United States might offer a quiet acceptance of nuclearization for specific partners.

Ultimately, rather than suggesting an imminent shift in official doctrine, the growing number of discussions on friendly proliferation highlights the mounting challenges of upholding nonproliferation standards in an increasingly dangerous strategic environment. This trend reflects a broader reconfiguration of U.S. foreign policy priorities and the shifting dynamics of alliance management in 2026, underpinned by a decline in allied trust in U.S. security commitments.
 

Explaining Friendly Proliferation Drivers: Expert Perspectives on Geopolitical Pressures and Institutional Erosion

Traditionally, the United States has approached its nonproliferation policy not merely as a normative commitment, but as a strategic interest managed through a carrot-and-stick approach. Three pillars designed to safeguard U.S. national interests anchor this policy: (1) politico-military tools like extended deterrence, which limit the appeal of proliferation by granting security guarantees to allies; (2) multilateral instruments, primarily the NPT, which serve as tools to universalize nonproliferation and provide a legal framework for containing adversaries; and (3) domestic guardrails, including legal instruments such as the Atomic Energy Act and bureaucratic processes that ensure policy durability.

Expert perspectives shared throughout this study indicate that the friendly proliferation debates signal a fundamental questioning of all three pillars. The focus on friendly proliferation has emerged from rapid changes in U.S. foreign policy that are forcing a reevaluation of traditional security trade-offs. Analyzing these pressure points—as mapped out by the interview cohort—is essential to understanding potential policy adaptations. In the view of many of the experts interviewed for this report, and particularly those representing the nonproliferation orthodoxy, such a shift would be a suboptimal solution that would ultimately jeopardize the very U.S. national interests which the current regime was designed to protect.

Extended Deterrence Under Pressure: Strategic, Credibility, and Budgetary Questions

The perception that extended deterrence is under strain due to growing Chinese and Russian threats has fueled the argument for friendly proliferation. In fact, the concept of friendly proliferation has flourished within the framework of China-focused defense studies. Many experts grappling with the two nuclear peer debate acknowledged that extended deterrence is the central variable in this equation. Initially, friendly proliferation was discussed primarily as a means to empower Asian allies and complicate China’s strategic calculus, though discussions also included considerations of Russia’s existing threat or coordinated actions with China.

In this study, 15 participants suggested that policymakers might contemplate the conceptual shift if the U.S. nuclear infrastructure is deemed insufficiently flexible, or to be in a state of “strategic inferiority” in terms of the number and diversity of nuclear weapons when facing China and Russia simultaneously. In this logic, friendly proliferation would allow allies to solve the math by providing their own deterrence, thereby freeing U.S. assets to focus on the broader two-peer problem. Several (4) respondents identified a Taiwan contingency as the potential breaking point—a stress test for U.S. strategy that could fundamentally call into question U.S. political willingness to risk a nuclear exchange for an ally.

However, despite these concerns, a majority of experts (24) did not believe that the Chinese nuclear buildup justifies advocating for friendly proliferation. This group argued that preventing nuclear spread remains a superior long-term logic. Some experts went so far as to contend that the most acute threat is not China’s nuclear buildup, but rather its conventional buildup, which is better countered through enhanced missile defense and long-range conventional strikes. Furthermore, some respondents cautioned that the U.S. community may be overemphasizing China’s role, noting that for countries where the pressure to proliferate is highest—such as South Korea—it is the regional threat of North Korea, rather than China, that drives the discussions.

However, since the concept of friendly proliferation emerged in the 2010s, recent challenges to extended deterrence have originated not only from adversary threats, but from allies who increasingly doubt the robustness of U.S. security guarantees. There is an overwhelming perception among the respondents (41 experts) that hedging against regional threats and abandonment is either currently occurring (8 experts) or imminent (31 experts). This shift, which has accelerated during the second Trump administration, shapes a more passive definition of friendly proliferation. In this scenario, the drive to proliferate is an allied response to a crisis of confidence in U.S. guarantees. Consequently, the U.S. reaction—ranging from firm opposition to silent acquiescence—would fundamentally shape the decisions of other allies contemplating a similar path.

Finally, the financial costs of U.S. extended deterrence are sometimes invoked to justify friendly proliferation. Among retrenchment advocates, proliferation is viewed not as a primary goal, but rather as a “lesser disagreement” compared to the costs of U.S. entanglement and overstretched guarantees. Some suggest this argument could prevail in a “black swan” financial collapse, where domestic ruin forces a choice between primacy and deterrence, making friendly proliferation a desperate exit strategy. However, the majority of experts interviewed—particularly those defending the current nonproliferation framework—viewed this financial rationale as insufficient, arguing that it overlooks both the underlying military logic and the positive economic repercussions of alliances that serve U.S. interests. Furthermore, these respondents emphasized that an ally would require significant U.S. protection during a development phase, lasting at least a decade—and potentially much longer depending on infrastructural readiness. This extended vulnerability window could prove more politically and financially costly than maintaining the current U.S. force posture abroad.

The Nonproliferation Regime: Institutional Erosion and the Shift Toward Transactional Implementation

The United States has historically been the foundational actor of the nonproliferation architecture, spearheading the defense of the NPT since the 1970s. This commitment has been grounded in three strategic principles: (1) the stabilization of international relations through limited nuclear spread; (2) the reduction of nuclear-use risks, whether intentional or accidental; and (3) the codification of order between nuclear and nonnuclear states. Today, however, friendly proliferation debates reflect a twofold destabilization of this regime.

First, the consensus regarding the efficiency of multilateral norms is eroding as transactional approaches increasingly define U.S. foreign policy. The U.S. strategic community is grappling with deeply divergent perceptions of the NPT’s long-term viability. Crucially, even those who argued for the treaty’s continued utility (26 experts) do not necessarily view it as an effective barrier to friendly proliferation; rather, they see it as an increasingly elastic framework that may no longer be capable of enforcing its original prescriptive intent. On the one hand, one group of experts (11 participants) warned that the shift toward relativist approaches creates a double standard that could trigger a rebellion among Non-Aligned Movement states. They further noted that China and Russia are already exploiting ambiguities within the treaty to frame U.S. extended deterrence as illegal—a move that threatens to weaken the NPT’s authority. On the other hand, more pragmatically oriented views are growing: 9 experts suggested that most states will not sacrifice security for a treaty, while 13 believed that the NPT will only survive if the United States justifies it as a tool that directly serves national interests. This more fragmented, interest-based assessment of the nonproliferation regime by the U.S. expert community highlights the challenges to the NPT’s future viability.

Second, this broader institutional shift is compounded by a more specific, shallower approach to U.S. implementation of nonproliferation policies, particularly regarding the NPT’s third pillar (peaceful uses of the atom). There is a growing perception that U.S. “red lines” regarding sensitive technology transfers are moving toward a logic of selective and transactional permissiveness (33 experts). The primary trend observed is the erosion of the traditional policy of denying allies access to enrichment and reprocessing (ENR) technology. A majority of respondents (23) believed that this line is vanishing, as evidenced by recent negotiations with South Korea (Republic of Korea, ROK) on nuclear-powered attack submarines (see text box below) and the Trump administration’s November 2025 joint declaration on nuclear cooperation with Saudi Arabia. These instances suggest that the United States may be willing to trade fuel-cycle access for industrial incentives or for a competitive edge in the Nuclear Energy Renaissance. This marks a significant departure from the traditional approach of limiting technology transfers because of proliferation risks, fueling a perception of a more permissive environment.

While U.S. policy appears to be loosening, a critical nuance remains: At least five experts pointed out that the second Trump administration is employing a tiered approach to this loosening, in which strict prohibitions are maintained for states deemed “risky,” such as Taiwan, Ukraine, or the Baltics, and lines are blurred for those states considered less risky. For the frontline states, the United States continues to enforce traditional red lines, fearing that any advancement toward latency could invite rapid escalation.

Ultimately, the expert opinions offered here suggest that an exclusively case-by-case approach could weaken the traditional U.S. policy that combines civil nuclear and security incentives to prevent proliferation among allies. The ultimate risk lies in the fragmented oversight of civilian nuclear cooperation, especially as decisions increasingly shift to a small group of senior officials, bypassing the standard bottom-up administrative process discussed below. Without this broad institutional vetting, the United States may lose the big-picture view needed to catch subtle signs of an ally’s intent to proliferate. Moreover, particularly regarding deals like the U.S.-ROK submarine agreement, participants noted that misaligned expectations could lead to a breach of commitment if either party feels its strategic goals are unfulfilled.

Political and Institutional Changes: The Attrition of Traditional Nonproliferation Guardrails

Historically, the United States’ nonproliferation policy has been anchored by a robust interagency process that functioned as a deliberate and slow-moving filter for policy shifts. This process—primarily involving the Departments of State, Defense, and Energy, and including the National Nuclear Security Administration (NNSA)—has acted as a series of institutional brakes overseen by career experts and legal advisers. These actors have ensured that policy remains consistent with long-standing diplomatic objectives, NPT commitments, and federal nonproliferation laws.

Moreover, congressional statutory authority regarding sanctions remains a hard constraint on the executive branch. Through legislation like the Atomic Energy Act and the 1994 Nuclear Proliferation Prevention Act, Congress has institutionalized U.S. nonproliferation policy by mandating specific penalties for proliferation, including the automatic triggering of economic and military sanctions against any state—even allies—that violates nuclear safeguards or tests a device. By making these consequences a matter of U.S. law rather than just executive preference, Congress ensures that nonproliferation remains a rigid requirement of U.S. foreign policy.

While these domestic guardrails persist, the interagency process overseeing them has undergone a significant transformation since the beginning of the second Trump administration, driven largely by the combination of a reduction in institutional capacity; a shift toward a highly centralized, administration-focused foreign policy apparatus; and a correlated lessening in the effectiveness of traditional diplomatic channels. First, the restructuring of the executive branch under the second Trump administration has led simultaneously to a reduction in specialized multilateral bureaus and a decline in nonproliferation funding, often in favor of modernization and deterrence programs. Consequently, the specialized nonproliferation arm of the State Department and the technical oversight roles of the NNSA have lost their potency, leaving the traditional defenders of nonproliferation marginalized. A vast majority of respondents (35 experts) believed that these bureaucratic processes are currently nonexistent, “hollowed out,” or, at a minimum, significantly weakened. This institutional attrition has also resulted in a generational and functional gap. As the experts who constructed the post-1960s nuclear order retire, a void is emerging. Specifically, the next generation is not entering the bureaucratic practitioner space due to diminishing opportunities, leading to a permanent loss of the technical expertise required to manage complex multilateral regimes.

Second, this bureaucratic erosion has facilitated a more administration-centered and heterodox decisionmaking environment. Respondents frequently cited President Trump’s October 2025 announcement to resume nuclear testing as a key example of this shift toward a decisionmaking process that simultaneously bypasses and marginalizes traditional interagency vetting. In the second Trump administration, decisions that once originated from career-level assessments are increasingly concentrated within a small circle of advisers in the White House or the National Security Council. This structural shift fuels the perception that friendly proliferation—which, as discussed above, is advocated by only a minority—could find a direct pathway to the highest spheres of power. In fact, over half of the expert respondents (25) believed that any departure from traditional nonproliferation doctrine is inextricably linked to the MAGA political orbit, going so far as describing such departure as the primary vehicle for individuals who favor retrenchment or the dismantling of the foreign policy status quo.

Finally, in the view of the experts interviewed here, the perception by U.S. allies and partners that U.S. foreign policy is increasingly driven by an insular group of heterodox actors seems to have compromised the effectiveness of traditional diplomatic channels. Allies and partners appear to now face significant uncertainty regarding the optimal mode of engagement with Washington on nuclear matters. In fact, this report’s findings on whether partners should proactively address friendly proliferation with the administration reveal a profound apprehension regarding adverse signaling risks (see Table 4). A notable segment of the strategic community interviewed expressed concern that direct dialogues with allies could inadvertently serve as a catalyst for radical policy shifts by the United States, essentially legitimizing fringe concepts through the mere act of discussing them. In addition, some experts warned of a misalignment of strategic intent: An ally attempting to utilize a proliferation threat as a bargaining chip for enhanced security guarantees might find their bluff unexpectedly validated, resulting in an unintended U.S. endorsement of their nuclear pursuit.

Recommendations: Addressing Friendly Proliferation Challenges to Secure U.S. and Allied Interests

The evidence presented thus far suggests that pressures on extended deterrence, a more transactional approach to multilateral norms, and shifting institutional dynamics within the United States and its government are collectively weakening the traditional nonproliferation consensus. While this study centers on the United States due to the country’s pivotal role within the nonproliferation architecture, these same factors are increasingly shaping strategic reflections within allied and partner countries as well. In this regard, it would be valuable for future research to examine how European and Asian allies perceive the U.S. friendly proliferation debate and how these external signals interact with their own domestic security dialogues.

Ultimately, the challenges posed by the friendly proliferation debate cannot be addressed by Washington in isolation. The findings of this research point toward a necessary dialogue between the United States and its partners to move away from unpredictable, case-by-case interactions and toward a more transparent and institutionalized model of alliance management.

Revitalize Intellectual and Institutional Frameworks in the United States and Abroad

First, on the intellectual front, the United States and its allies and partners must produce a contemporary defense of the tools and norms comprising the current security landscape by:

• Reviving track 1.5 dialogues between officials and bipartisan researchers to bridge the gap between theoretical grand strategy and practical implementation. These dialogues could be convened domestically, inside each allied country. They should also progressively become multilateral, so that the United States and its allies can exchange views on contemporary challenges to nonproliferation.
• Financing research projects to empirically test the friendly proliferation hypothesis, including evaluating its effectiveness (or lack thereof) in specific military contingencies and its subsequent budgetary implications for the United States and its allies.

Second, on the institutional front, the United States and its allies should uphold existing assessment and oversight mechanisms, both domestically and internationally. Domestic institutional resilience, in particular, will be critical to pursing a fruitful assessment of contemporary risks to U.S. nonproliferation policy. In this regard, it will be paramount to:

• Maintain organizational capacity to assess proliferation risks by ensuring that specialized bureaus are adequately staffed and funded to provide thorough assessments of potential proliferation crises. Decisionmaking should systematically integrate regional and functional experts to dismantle potential institutional silos and ensure that deterrence requirements do not override nonproliferation imperatives.
• Assert congressional oversight, in particular by encouraging members of Congress to proactively exercise their constitutional prerogatives through regular briefings and hearings on the drivers of friendly proliferation. By leveraging the oversight powers of the Senate Foreign Relations and House Foreign Affairs Committees in particular, the legislative branch can act as a necessary institutional check, ensuring that shifts in nonproliferation policy are transparent, debated, and grounded in long-term national security interests rather than contingent executive directives.

Internationally, institutional frameworks within alliances meant to discuss nonproliferation must be kept alive, potentially tackling concerns regarding friendly proliferation directly via:

• Bilateral strategic dialogues on nonproliferation that contribute to shared threat assessment and concerns.
• Multilateral bodies dedicated to discussing these issues. For instance, in NATO, the Arms Control, Disarmament and Non-Proliferation Committee—the senior body for discussion of the alliance’s efforts against the proliferation of weapons of mass destruction—could convene discussions on issues related to friendly proliferation if deemed necessary by allies.
   

Clarify Commitments and Preserve Mutual Trust

Because the risk of friendly proliferation could be driven by an ally's fear of abandonment by the United States, Washington must restore predictability through unequivocal signaling and strengthened security guarantees. While the second Trump administration’s diplomatic posture may resist traditional multilateral constraints, the following unilateral actions on the part of the United States would provide a solid foundation to repel proliferation incentives among allies.

• Issue explicit declaratory policy against friendly proliferation. Washington must formally clarify that the “friendly” nature of an ally would not exempt them from the legal, political, and economic responses provisioned by U.S. tools and norms against proliferation. This is necessary to dispel the growing illusion in allied capitals that a nuclear pursuit could be negotiated without triggering U.S. sanctions, or at least have few consequences.
• Formalize the linkage between extended deterrence and nonproliferation. The United States should explicitly reiterate that its security guarantees are contingent upon a partner’s continued commitment to nonproliferation. This could be done with high-level joint statements in which nuclear hedging would be defined as a threat to operational viability, and warning that a nuclear path would technically—and practically—dissolve U.S. security guarantees.

In addition, in multilateral formats, the United States and its allies should collectively:

• Raise the priority of difficult conversations within existing extended deterrence mechanisms. In Europe, this could be done within the NATO framework, either through the Nuclear Planning Group or other formats inclusive of France. In Asia, existing bilateral frameworks—the S.-ROK Nuclear Consultative Group, U.S.-Japan Extended Deterrence Dialogue, and AUKUS (Australia, United Kingdom, United States) Pillar 1—should be utilized; tri- or quadrilateral formats could further diffuse regional tensions on the topic of friendly proliferation in the region.
• Bolster these dialogues through tabletop exercises that simulate specific regional contingencies involving an allied nuclear pursuit. This would better allow officials to assess domestic concerns and risks while raising awareness regarding escalation dynamics and the potential lowering of the nuclear-use threshold.
• Leverage alliance-level public diplomacy to clarify the goals and existing benefits of extended deterrence. Communication strategies could be channeled through established multilateral bodies, such as NATO’s Public Diplomacy Division, to clarify how extended deterrence functions and promote awareness in allied countries regarding the risks of indigenous nuclear programs. Such communication would emphasize that a move toward proliferation would technically and politically decouple a country from the collective security framework NATO provides.
• Use public diplomacy to differentiate nuclear sharing from proliferation. This would include prioritizing joint research projects and public messaging that clearly distinguish legitimate nuclear sharing from proliferation. This clarification would both prevent adversaries from intentionally conflating the two in multilateral disarmament fora and help allies maintain a unified front.
• Harmonize domestic narratives regarding the risks of proliferation. Conveying a consistent message to all constituencies—domestic and international—of an alliance would durably reduce the appeal of concepts like friendly proliferation, particular if they are presented as threats to the unity and deterrent power of the entire alliance rather than as viable national solutions to a security problem.
   

Realign Nuclear Energy Policy and Nonproliferation Standards with Allies and Partners

To prevent nuclear hedging risks, civil and military nuclear cooperation must be more explicitly and systematically tied to nonproliferation commitments. In the case of existing agreements, such as the U.S.-ROK submarine deal, the United States should convene extensive bilateral dialogues to alleviate risks of misunderstanding. These dialogues must explicitly signal that technological cooperation in specific military or civil niches does not represent a permissive shift toward accepting allied nuclearization.

For future cooperation, negotiations should:

• Be tied to a systematic assessment of proliferation risks, signaling that Washington prioritizes NPT compliance as a baseline for any technology transfer.
• Include explicit, public references to Section 123 Agreement requirements in all official declarations regarding nuclear energy cooperation. While these legal requirements under the Atomic Energy Act exist regardless of rhetoric, consistently highlighting the “gold standard”—i.e., the renunciation of enrichment and reprocessing—serves as a vital signaling tool. By making these legal constraints a central part of the public narrative, the United States would clarify to both partners and the international community that it has no intent to bypass the rigorous nonproliferation standards that underpin its nuclear exports.

Conclusion

This report examines the transition of friendly proliferation from a fringe academic theory to an increasingly mainstream debate within the U.S. strategic community. While a broad consensus favoring traditional nonproliferation persists among experts, conceptual discussions regarding allied nuclearization have reached their highest level since the Cold War.

Friendly proliferation—the potential long-range implications of which are poorly specified or understood—remains too underdeveloped to provide the policymaking community with the rigorous tools required to resolve today’s strategic dilemmas. Nonetheless, these debates highlight the implications of the major movements questioning U.S. nonproliferation policy in 2026 and under the second Trump administration.

Debates around friendly proliferation highlight critical systemic vulnerabilities for the United States and the international community, starting with the fact that strategic pressures from the two-peer problem and mounting budgetary concerns are placing strain on the traditional “Grand Bargain”—the foundational trade-off in the NPT between nuclear and nonnuclear signatories—involving, in particular, extended deterrence guarantees and nonproliferation commitments. While these pressures are not currently sufficient to trigger the adoption of proliferation as official doctrine or U.S. policy, they are driving a more transactional approach to alliances. Moreover, the pervasive apprehension among allies regarding the reliability of the U.S. nuclear umbrella could pave the way for a move toward “silent acquiescence” should an ally choose to pursue an indigenous deterrent. In addition, the erosion of a universalist approach to the NPT in favor of case-by-case dealmaking risks hollowing out a regime that serves as a vital institutionalization of U.S. national interests. This shift is compounded by institutional attrition within the interagency process, which is allowing fringe concepts to bypass traditional technical filters and reach the highest spheres of power.

To address the challenges posed by the friendly proliferation debate, this report proposes a restoration of predictability through a shared alliance-wide roadmap. This requires Washington and its allies to uphold existing institutional means to inform high-level decisionmaking with technical expertise while engaging in collective consultative spaces to facilitate frank dialogue. Simultaneously, the United States and its allies must collectively provide unequivocal signaling opposing nuclear proliferation—by allies and adversaries—and making it clear that indigenous nuclear pursuits would technically and politically decouple an ally from collective security frameworks. Ultimately, this messaging should be backed by a realignment of nuclear energy policy and nonproliferation standards both domestically and internationally.

While this trajectory faces significant pitfalls—including domestic political polarization in the United States and strengthening pro-nuclear armament constituencies in allied capitals—reanchoring alliances in institutional expertise and clear strategic commitments remains essential. Through this path, Washington and its allies could prevent the friendly proliferation debate from evolving into a self-fulfilling prophecy that dismantles the alliance systems that have underpinned global stability for three-quarters of a century.

Astrid Chevreuil is a visiting fellow in the Europe, Russia, and Eurasia Program at the Center for Strategic and International Studies in Washington, D.C.

Acknowledgments

I would like to express my sincere gratitude to Max Bergmann for placing his trust in me to conduct this study within his program, and for his careful review of the report.

I am deeply grateful to Toby Dalton, Jamie Kwong, Donatienne Ruy, and Heather Williams for their insightful peer reviews, which substantially improved the final product. My heartfelt thanks also go to Tara Varma for believing in this project from its inception and for her encouragement to pursue it.

Finally, I would like to thank Mickaël B. for taking care of our daughter during most of the interviews, and for his constant, invaluable support throughout this journey.

This report is made possible by general support to CSIS. No direct sponsorship contributed to this report.

Please see the PDF for the appendices.