Any such a deal is likely to go down badly in Washington as Western countries seek to keep up the pressure on Iran to agree a comprehensive deal on its nuclear activities.
Sergei Chemezov, head of the Rostec corporation which manages Russia's defence industry, said Moscow has offered to supply Antey-2500 missiles, an upgraded version of the S-300 air defence system that figured in the previous contract.
"We have offered them the Antey-2500," Chemezov was quoted as saying by RIA-Novosti news agency.
Moscow signed a contract in 2007 to deliver S-300 missiles to Iran worth USD 800 million.
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The deal was intensely criticised by the United States and Israel, and Moscow later dropped it as being in breach of UN sanctions.
A UN resolution adopted in 2010 bans the supply, sale or transfer to Iran of missiles or missiles systems.
Chemezov said the Antey-2500 is a more modern version of the S-300, which Russia no longer makes. The same surface-to-air missiles were reportedly delivered to Venezuela in 2013.
Now under Western sanctions itself over the conflict in Ukraine, Russia -- a permanent member of the UN Security Council -- has strengthened its alliance with Iran.