Russian Foreign Minister Sergei Lavrov said Russia's proposal is motivated by a "will to help."
The ITAR-Tass news agency quoted the Iranian President Mahmud Ahmadinejad as casting doubt on the idea in a speech on 2 February.
The European Union and the United States have backed Russia's proposal to enrich uranium for Iran as a possible way out of the impasse over its disputed nuclear program.
The 35-member governing body of the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), is bracing itself to decide to report Iran to the UN Security Council over its nuclear program.
The IAEA talks are currently being held behind closed doors in Vienna.
(AP)