Iran denied on Sunday that it had received a proposal from Russia, which announced on Saturday that it had sent the formal plan to Tehran.
But a Russian diplomat on Monday again said that a formal plan had been sent.
According to Interfax, Vyacheslav Moshkalo, a diplomat at the Russian embassy in Tehran, said: "We presented an official memo to Iran on Saturday. We are waiting for a reply."
The Foreign Ministry in Moscow declined to comment but said in a statement that a meeting took place on Monday between Gholamreza Ansari, the Iranian ambassador, and Alexander Alexeyev, Russia's deputy foreign minister.
The two nations' contradictory statements may be the result of an Iranian attempt to gain time without directly rejecting a proposal from Moscow, a long-standing ally.
Uranium enrichment is a key step in the nuclear process that produces either fuel for a reactor or the material needed for a warhead.
The United States has accused Iran of seeking to develop nuclear weapons. Iran says that its programme is directed only at generating electricity.
"We presented an official memo to Iran on Saturday. We are waiting for a reply"
Negotiators from Germany, France and Britain want to solve the dispute by having enrichment moved to Russia to ensure that Iran cannot divert uranium to a weapons programme. But Tehran has said it will not agree to moving enrichment abroad.
Russia's Foreign Ministry said on Saturday that its formal proposal represented a "Russian contribution into the search for mutually acceptable solutions in the context of settling the situation around the Iranian nuclear programme by political and diplomatic means".
Washington is pushing for Tehran to be brought before the UN Security Council, where it could face economic sanctions over the dispute.
But Russia and China, which have vetoes on the council, oppose referral, and the West has stopped short of forcing the matter.
Russia is building a nuclear power plant in Iran in a deal that has drawn strong US criticism.