In an interview with German weekly Spiegel, Medvedev confirmed Russia was prepared to help with work in enriching Iranian uranium if Tehran agreed to a UN-brokered plan to break the deadlock.

"If the Iranian leadership takes a less constructive position, then in theory anything is possible," Medvedev said in the interview, a full transcript of which was released by the Kremlin.

"I do not want that all this ends up with the adopting of international sanctions because sanctions, as a rule, lead in a complex and dangerous direction.

"But if there is no movement forward then no-one is going to exclude such a scenario."

Russia -- a permanent veto-wielding member of the UN Security Council -- is seen as a key player in the Iranian nuclear crisis due to its close political and economic ties with Tehran.