According to news reports, Russian President Vladimir Putin signed a decree yesterday lifting the ban on export and delivery of S-300 air defense systems to Iran. The decree essentially eliminates restrictions that have been in place since 2010, when Russia cancelled a contract to sell such systems to Iran, citing the desire to support the international sanctions regime against Iran’s nuclear program. By eliminating such restrictions, the decree paves the way for future sales of the S-300, although the two states would presumably still have to reach agreement on a new contract. Nor would the sale of those systems violate the international sanctions regime against Iran, since Russia specifically negotiated an exception to that regime permitting the sale of ground-to-air missiles to Iran. U.S. State Department spokesperson Wendy Harf has acknowledged as much.

Putin’s actions were not a total surprise, since there have been indications recently that the two states were seeking to reconstitute the sale. In January of this year, Russia and Iran jointly announced a new agreement for expanding their military relationship. The announcement was accompanied by statements that the two were also working to settle disputes arising out of cancellation of the original S-300 contract. In February, Sergei Chemezov, the head of ROSTEC, who is responsible for overseeing Russian arms transfers, was quoted by Russian news agency TASS as saying that Russia was now willing to supply Tehran with the Antey-2500 air defense system, which is an improved variant of the S-300 system that was originally offered.

By moving ahead with the sale at this time, Putin is likely seeking to cement Russia’s position as Iran’s preferred arms supplier before Western arms embargoes are lifted, in which case it would likely face stiffer competition. Prior to 2010, Russia had been Iran’s primary arms supplier, and with Iran eager to modernize its military, Russia hopes to favorably position itself to capture as much of the Iranian market as possible.

Were the sale of the Antey-2500 to be completed, Iran would receive an air defense system significantly more capable than any it currently has in place. The Antey-2500 is designed to defend against a range of aerial targets including fixed-wing aircraft, tactical ballistic and cruise missiles, airborne early warning aircraft and other airborne platforms. The system offers a number of improvements over the previously-offered S-300 model, including a better engagement radar and upgraded surface-to-air missiles. In short, this new system would provide better range, greater survivability, superior performance, and in short enhanced protection for Iran’s territory.

Clearly, the S-300 would significantly enhance Iran’s air defense capabilities, as such systems are deemed to be effective even against advanced U.S. or Israeli strike aircraft. Still, the sale of a small number of S-300 systems will not be sufficient in and of itself to alter the overall balance. Advanced U.S. aircraft, especially stealthy aircraft like the F-22, will remain capable of penetrating Iran’s airspace, and the United States retains the ability to suppress or destroy the new air defense systems over time. Nevertheless, if the sale goes through, newly deployed S-300 systems would make any effort to strike Iran’s nuclear infrastructure significantly more challenging.

Paul N. Schwartz is a senior associate with the Russia and Eurasia Program at the Center for Strategic and International Studies in Washington, D.C.

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Paul N. Schwartz