Russia regrets that Iran has apparently rejected a UN-brokered nuclear fuel exchange deal to ease the standoff over its atomic programme, Foreign Minister Sergei Lavrov said on Friday.

"We regret that Iran -- as far as we can see -- does not consider it possible to agree to the formula that it was offered," Lavrov told a news conference.

Under the plan, Iran would hand over most of its stocks of low-enriched uranium in return for the supply by France and Russia of nuclear fuel enriched to the higher level required for a Tehran research reactor.

Russia, a veto-wielding permanent UN Security Council member, is one of the few major powers to have close relations with Iran.