Five congressmen said the companies violate U.S. laws banning arms deliveries to Tehran and Damascus.
Russia has said all its arms deliveries to the two Mideast nations are in line with international laws, but U.S. authorities have repeatedly called on Russia to stop arms deliveries to countries Washington considers a threat.
President Vladimir Putin said in October that Russia will not allow other countries to put restrictions on its arms exports.
Speaking at a session of Russia's military-technical cooperation commission, the president said Moscow would not take into consideration attempts to impose restrictions "based on unilateral and politicized assessments".
Putin also said deliveries of Russian weapons are aimed exclusively at increasing the defense capability of the countries receiving them, and at maintaining their stability.
Russia and Iran concluded a contract in late 2005 for deliveries of Tor-M1s. Tor-M1 is a high-precision missile system designed to destroy manned or unmanned aircraft, as well as cruise missiles flying at an altitude of up to 10 kilometers (6 miles). Russia subsequently supplied 29 Tor systems to Iran for $700 million.
Syria, a long-time client of Russia's defense industry, accounts for up to 4% of Russia's annual arms sales, which totaled a record $6.1 billion last year.
