It has been reported that Russia has proposed the sale of S-300 surface-to-air missile defense systems to Iran. According to the Russian News Agency TASS, Russian Foreign Minister Sergey Lavrov said that Russia’s previous voluntary embargo of sales of military equipment to Iran is no longer needed due to the progress in the negotiations regarding Iran’s nuclear program.

On May 1, 2015, Ed Royce (R-Calif.), the Chairman of the House Foreign Affairs Committee, and ranking member Eliot Engel (D-N.Y.) sent a letter to President Obama stating that the White House should consider using sanctions to deter the delivery of the missile defense system to Iran. The letter calls on the President to determine whether the proposed sale would advance Iran’s efforts to acquire or develop destabilizing numbers and types of advanced conventional weapons.

Although the letter does not specifically reference the relevant provisions of U.S. law, it appears the Congressmen have in mind the Iran-Iraq Arms Nonproliferation Act, which provides for the imposition of sanctions on any person who “transfers or retransfers goods or technology that would contribute knowingly and materially to the efforts by Iran . . . to acquire destabilizing numbers and types of advanced conventional weapons.” Such sanctions would prohibit, among other things, the issuance of export licenses to such a person for two years. Section 6(b) of the Iran Sanctions Act of 1996 includes similar language requiring sanctions on persons who have exported or transferred, or permitted or otherwise facilitated the transshipment of, any goods, services, technology, and knew or should have known that it would contribute materially to the ability of Iran to “acquire or develop destabilizing numbers and types of advanced conventional weapons.” The possible sanctions under that law include prohibitions on export-import bank assistance, export licenses, loans from U.S. financial institutions, transactions in foreign exchange, banking or property transactions, and investment in equity or debt of the person. These laws potentially could serve as a basis for new sanctions on Russian entities and individuals involved in the sale of the missile systems.

Meanwhile, although the State Department expressed concern over the transaction because of Iran’s recent conduct in the region, it stated that it did not believe the transaction would have an effect on the unity of the United States and Russia in their negotiations with Iran on its nuclear program.

This situation highlights the fragile and complex interaction between the ongoing negotiations with Iran and U.S. relations with Russia.