The US and the EU are reportedly proposing to grant Iran the right to continue a limited nuclear programme.
Iran faces the threat of sanctions if it does not halt its nuclear plans
Unnamed officials say the compromise would allow Iran to convert uranium into gas, as it has since August.
But enriching the uranium, at which point weapons-grade material could be produced, would be done in Russia, before energy was transferred to Iran.
Iran insists it has the right to pursue a nuclear energy programme, and is yet to signal if it will accept the offer.
The director of the International Atomic Energy Agency (IAEA), Mohammed ElBaradei, said on Thursday he was optimistic a solution was close at hand.
"He hopes that in the coming days the international community will be able to coalesce around a solution that is acceptable to all parties, including Iran," an IAEA spokeswoman said.
Earlier this week, Mr ElBaradei proposed creating an international stockpile of nuclear energy to remove the need for individual states to purse so-called "dual-use" nuclear programmes.
Reports of the US-EU deal came days after a secret letter from Iran to the IAEA appeared to restart the diplomatic process, conducted by the UK, Germany and France - the EU3 - on behalf of the European Union.
Mohamed ElBaradei has attempted to broker a compromise deal
Talks broke down in August when Tehran resumed the processing of uranium at its plant in Isfahan.
A Russian government spokesman, Nikolai Shingaryov, told the Agence France Presse news agency that Russia had approached Iran with the new proposal, but had received no response.
The two countries enjoy close co-operation on nuclear issues, and Russia is aiding Iran on its new nuclear reactor at Bushehr.
But unnamed US and EU officials close to the talks said they were sceptical that Tehran would agree to the proposals.
Iran could view the plan as a surrender of its right to enrich uranium within its own borders, correspondents say.
Alternatively it could contend that it retains the notional right, but has merely chosen to enrich uranium at foreign facilities.
"What ElBaradei said may be wishful thinking," a European official told the Reuters news agency.
"Perhaps the Iranians will make a deal with us, but I think we will be surprised if that happens."
The US, which contends that Iran aims to build an atomic weapon, has threatened to take Tehran to the United Nations Security Council.
An IAEA resolution passed in September paved the way for Iran's referral to the Security Council, but the agency has not set a date for this.
Iran maintains it is only seeking to develop a civilian nuclear programme.