Russia has offered to sell Iran its state-of-the-art Antey-2500 surface-to air-missiles, the head of Russian state defence conglomerate Rostec said.
In 2010, the US and Israel argued that the S-300 rockets could be used to shield Iran's nuclear attacks from air strikes, and Moscow dropped the offer.
Tehran subsequently launched a $4bn (£2.6bn) lawsuit against Russia in Geneva for reneging on the deal but the countries remain allies.
The Antey 2500 is an updated version of the S-300 and travels at 4,500m per second with a 2,500km (1,500 miles) range, according to Almaz-Antey, the company that makes them.
Sergei Chemezov told Russian state news agency TASS: "As far as Iran is concerned, we offered Antey-2500 instead of S-300. They are thinking. No decision has been made yet."
The system has already been sold to Venezuela and Egypt, report Russian state media.
Russia has courted controversy by offering to sell Syria's president Assad S-300s.
In January, Russian President Vladimir Putin said Russia's arms exports in 2014 had hit $15bn, and Chemezov said the conflict in the Middle East had helped fuel the surge in sales.
"I don't conceal it, and everyone understands this, the more conflicts there are, the more they buy off weapon from us. Volumes are continuing to grow despite sanctions. Mainly, it's Latin America and the Middle East," he was quoted as saying.
Chemezov was one of a number of Putin's inner circle blacklisted by the US government following Russia's annexation of Crimea in 2014.