"Whether the plans will be realised depends on many factors," a statement from the Russian Atomic Energy Ministry said.

The move is an apparent concession to United States Energy Secretary Spencer Abraham, who said on Thursday that the matter was of the "utmost" concern to the US.

Abraham: concerned about Iran's intentions

Last week Moscow surprised Washington by announcing a 10-year nuclear co-operation accord with Iran - one of three countries denounced by President George Bush as an "axis of evil".

The US has long opposed Russia's involvement in the construction of a nuclear power plant at Bushehr in southern Iran, and the new accord includes provision for further plants to be built.

The Russian Government programme "merely talks about the existing technical possibilities," the statement read. "Their implementation will depend on many factors, including political."

'Many factors' involved

The statement follows three days of discussions between Russian energy ministers and Mr Abraham in Moscow.

The talks were largely devoted to Russia's co-operation plan with Iran to build five new nuclear reactors.

We consistently urge Russia to cease all nuclear co-operation with Iran, including its assistance to the reactor in Bushehr

Spencer Abraham

In response to US accusations that Russia's ties with Iran were helping advance its nuclear weapons programme, the atomic energy ministry said any nuclear deal was limited to building the reactor in Bushehr.

On Thursday, Mr Abraham said he was deeply worried by Russia's decision to expand its projects in Iran.

"We consistently urge Russia to cease all nuclear cooperation with Iran, including its assistance to the reactor in Bushehr," Mr Abraham said.

His message was reaffirmed by US Under-Secretary of State John Bolton, who was also present at the discussions in Moscow.

Mr Abraham accused Iran of "aggressively pursuing nuclear weapons as well as weapons of mass destruction".

Civil atomic energy projects would only fast-track the country's nuclear weapons programme, he warned.

US officials argue there can be no other reason for a country with Iran's oil resources to want so many nuclear power reactors.

New nuclear deal

The accord between Russia and Iran came as a surprise to US officials. In the wake of 11 September, Russia emerged as one of America's key allies in its anti-terror campaign.

Iran's nuclear capabilities are in the spotlight

Less than a month ago, Moscow even agreed to a confidence-building $20bn aid package for dismantling Russia's weapons of mass destruction.

But the BBC's regional affairs analyst Steven Eke says the issue of Russia's nuclear co-operation with Iran is one of the most contentious problems in US-Russia relations, and the reactor at Bushehr is at the heart of the problem.

The plant should be running within two or three years and, while Moscow insists it has adequate controls in place, previous failures have provoked suspicion in the US.

The reactor itself could not be used to make a nuclear bomb, our correspondent says, but weapons-grade plutonium could theoretically be extracted from its spent fuel.

The nuclear issue is part of a wider strategic disagreement between Washington and Moscow over Iran.

Russia has derided the idea that Iran belongs to what President Bush calls "the axis of evil" - and has even accused Washington of orchestrating an anti-Iranian campaign.