The head of the UN's International Atomic Energy Agency has said Russia's nuclear co-operation with Iran is no longer a matter of concern.
The US has urged Russia to halt construction at Bushehr
After talks in Moscow with President Vladimir Putin, Mohamed ElBaradei said Russia's construction of Iran's first nuclear reactor was not even discussed.
He denied US claims that the Bushehr reactor could be used to make weapons.
The statement came after IAEA experts visited another site where the US says Iran worked on nuclear arms.
"Bushehr is not apparently at the centre of international
concern," Mr ElBaradei told reporters on Tuesday.
The IAEA chief said the reactor was aimed at producing nuclear energy only, and there was an agreement to return spent fuel to Russia.
"It is not something that is of any concern on our part," he added.
Mr Elbaradei said the reactor was not even mentioned in the hour-long meeting he had with President Putin.
The US - which says Iran has been running a secret nuclear weapons programme - has put pressure on Russia not to go ahead with the reactor in southern Iran.
Tehran says its nuclear programme is designed solely to provide energy.
Construction on the Bushehr reactor began in 2002, despite strong US objections.
Moscow denies any suggestion that Tehran could make a bomb on the basis of the nuclear technology it is making available.
The reactor is due to become operational in 2005.
Mr Elbaradei also said that Iran had provided details about another site at the centre of American allegations.
He said Iranian officials had told an IAEA team that the Lavizan site in Tehran was initially used for military research - but not nuclear weapons as the US suspects - before it was razed.
"The Iranians said it was a former research and development military site and was used as a physics institute, later for
bio-technology research," Mr ElBaradei said.
The Americans say the site has been completely dismantled and the topsoil removed in the past year, to try to hide evidence of nuclear activity.
Iranian officials say the site was razed to make way for a park.
International inspectors visited the site on Monday.
Mr ElBaradei expressed satisfaction with Iran's co-operation with the inspectors - less than two weeks after his agency criticised Iran.