Russia's Defense Ministry said the sanctions were apparently a U.S. reaction to the sale of Russian weapons to Venezuela.
Officials at Sukhoi, Russia's top manufacturer of fighter jets, said the company had not sold equipment to Iran since the 1990s.
Rosoboronexport said the company only shipped defensive weapons to Iran in conformity with international law.
Last month, Russia sold Venezuela military aircraft in a deal estimated at up to $3 billion. The United States, which has banned arms sales to Venezuela, strongly criticized the deal.