Iranian and Russian officials meet in Moscow today to discuss a possible compromise deal over Iran's nuclear programme.
Moscow is offering to enrich the uranium Iran needs for nuclear power stations on Russian soil, an arrangement that would help ease international concerns Tehran could divert the material for bomb-making.
The arrival was kept low-key, with no Russian officials turning up at Moscow's Sheremetyevo airport to meet the Iranian delegation.
Members of the delegation declined to comment on the format or contents of their planned talks with counterparts from Russia's Security Council and its nuclear agency Rosatom.
The thinking behind Russia's proposal is that if it processes uranium for Iran, it could ensure the fuel was enriched only to the level suitable for power stations, and not to the higher grade needed for a nuclear bomb.
The United States and the European Union three of France, Britain and Germany - the countries pressing Iran hardest on its nuclear programme - have backed the Russian plan, but privately Western diplomats are sceptical Tehran will accept.
Iran says it has a sovereign right to carry out a full nuclear fuel cycle on its own soil but is willing to hear more about the Russian plan. Western diplomats say they believe Tehran is keeping the Russian offer on the table to buy time.