Top Russian officials were holding high-level talks in Iran over the Islamic republic's disputed nuclear programme amid a fresh drive to find a diplomatic solution to the worsening crisis.

Russian National Security Council chief Igor Ivanov speaks during a press conference after meeting with the head of the Iranian Atomic Energy Organization Gholamreza Aghazadeh in Tehran, in November 2005. [AFP]

Russian National Security Council chief Igor Ivanov and Deputy Foreign Minister Sergei Kislyak were meeting with top Iranian nuclear negotiator Ali Larijani, an AFP correspondent said.

They were also lined up for talks with Foreign Minister Manouchehr Mottaki and the head of Iran's Atomic Energy Organisation, Gholamreza Aghazadeh.

No details from the talks were immediately available, but the mission follows up on a meeting of senior officials from Britain, China, France, Russia and the United States -- the five permanent UN Security Council members -- as well as Germany that failed to break an impasse on how to deal with Iran although progress was reported.

A follow-up meeting at the foreign ministers' level is expected to take place in the coming week. US officials said it would probably take place in a European capital.

At their meeting in London last Wednesday, the major powers discussed a European proposal aimed at breaking Iran's determination to enrich uranium, a process which can be extended from making reactor fuel to nuclear weapons.

The EU proposal would combine technology, economic and other incentives for Iran, but also the threat of an arms embargo and other sanctions if the Islamic republic defied a UN injunction to halt enrichment.

Tehran has rebuffed the EU proposal, repeating that its right to enrich uranium was not negotiable.

Both Russia and China oppose talk of sanctions against Iran, which has consistently denied US claims that its nuclear programme is a cover for the development of atomic weapons.

Last year Russia offered to produce nuclear fuel on Iran's behalf in order to ease fears Tehran would divert uranium into warheads. Talks broke down when Iran insisted uranium enrichment had to be carried out on its soil.

As a signatory to the nuclear Non-Proliferation Treaty (NPT), Iran insists it has a right to uranium enrichment and has vowed not to back down on nuclear research and development.

"The Islamic Republic of Iran remains firm in its position, to use nuclear technology in a peaceful and legal framework," Iran's hardline President Mahmoud Ahmadinejad was quoted as saying in newspapers on Sunday.

"The position of Iran concerning the nuclear issue is totally legal and in the framework of the NPT," he said.

But there have been signs of compromise in the stand-off.

Iran's ambassador to the United Nations, Javad Zarif, said Friday that Tehran was willing to accept a cap on its uranium enrichment capability to ensure the fuel produced is not used to develop nuclear weapons.

And the New York Times reported Saturday that President George W. Bush's administration was beginning to debate whether to set aside a longstanding boycott of Iran and open direct talks to try to resolve the crisis.

The United States severed relations with Iran after the 1979 Islamic revolution and the crisis over the seizure of American hostages, and Bush in 2002 famously described Tehran as part of an "axis of evil".