The negotiations were seen as a last chance for a deal to assuage worries over Iran's nuclear ambitions ahead of a meeting on Monday of the UN watchdog International Atomic Energy Agency (IAEA) that will decide whether to refer Tehran to the UN Security Council for action.

The source said the talks had been concluded and the Iranian delegation by the country's chief nuclear negotiator, Ali Larijani, planned to fly back to Tehran on Thursday.

Larijani, for his part, reaffirmed Iran's insistence on its right to enrich uranium, which can be the fuel for nuclear reactors but also the material for atomic weapons.

"The enrichment process is the sovereign right of all states," he said.

"States that have a peaceful nuclear program must not be deprived of this right."

Iran had showed little inclination to compromise as the talks began.

Shortly after his arrival, Larijani had rebuffed calls for Iran to suspend uranium enrichment work, saying there was "no direct link" between reinstating a moratorium and reassuring the world over its nuclear ambitions.

"A moratorium is needed when there is something dangerous, but all of our activities are transparent," he said.

His comments suggested there had been little movement by Iran and Russia, which have met several times over recent weeks to try to head off referral to the Security Council, which can impose sanctions.

In a report earlier this week, IAEA chief Mohamed ElBaradei accused Tehran of failing to cooperate with the agency.

"We do not have any extraordinary demands," Larijani said, adding that Iran was still open to giving IAEA inspectors access to nuclear facilities provided their work was carried out in line with international law.

Russia is building Iran's first nuclear power plant as part of that nation's fledgling nuclear power program.

The United States accuses Iran of using that program to hide development of nuclear weapons, a charge Tehran vehemently denies.

Iran says it has a right to generate its own nuclear power like any other country, but the West says the fact that Iran hid parts of its nuclear program for 18 years and has called for Israel to be "wiped off" the map make it a special case requiring further verification.

Russian President Vladimir Putin said on the eve of the Moscow talks he was "optimistic" that Iran would return to compliance with the IAEA's "additional protocol," a contract designed to boost the agency's power to protect against secret weapons programs, notably through inspections.

Iran abided by that pact until late last year, when it announced plans to resume uranium enrichment and said IAEA inspectors were no longer welcome.

Russia and China, which both have extensive economic links with Iran, are anxious to prevent the issue from being sent to the Security Council, and the Russian plan, which centers on providing it with uranium enriched on Russian territory, is aimed at keeping the issue within the IAEA.

Speaking to reporters in neighboring Afghanistan, where he was on his first visit, US President George W. Bush made clear that the United States was not prepared to allow Iran to proceed unchecked with work that could lead to production of a nuclear weapon.

"Iran must not have a nuclear weapon. The most destabilizing thing that can happen in this region and in the world is for Iran to develop a nuclear weapon," he said at a news conference with Afghan President Hamid Karzai.

Bush reiterated, however, that he supported Russia's efforts to find a way out of the impasse.

Russian Foreign Minister Sergei Lavrov meanwhile said Iran's reinstatement of its moratorium on uranium enrichment was needed if progress were to be made ahead of the March 6 deadline.

Related Links
-