Iran says it only wants nuclear power for peaceful purposes
Iran's president has said it is ready to send its enriched uranium abroad for further enrichment under a deal to ease concerns about its nuclear programme.
Mahmoud Ahmadinejad told state TV that Iran would have "no problem" if most of its stock was held for several months before being returned as fuel rods.
Correspondents say that such a decision would be a major shift in Tehran's position.
The US said that if this was a new offer, it was "prepared to listen".
Last month, diplomats said Iran had informed the International Atomic Energy Agency (IAEA) that it did not accept the terms of the deal and had instead demanded a simultaneous exchange on its territory.
The US and its allies fear Iran is attempting to develop nuclear weapons. Iran insists its nuclear programme is entirely peaceful.
The deal agreed in October between Iran, the IAEA and the so-called P5+1 - the US, Russia, China, UK, France plus Germany - envisaged Iran sending about 70% of its low-enriched uranium to Russia and France, where it would be processed into fuel for a research reactor.
But for months, Iranian officials publicly criticised the terms and said they were unwilling to export the uranium without simultaneously receiving fuel in return. The proposal proved unacceptable to the West.
But in a television interview on Tuesday, President Ahmadinejad dismissed the concerns of his "colleagues" that the West would not return the uranium, saying Iran would respond by producing more.
"We have no problem sending our enriched uranium abroad," he said.
"We say: We will give you our 3.5% enriched uranium and will get the fuel. It may take four to five months until we get the fuel.
"If we send our enriched uranium abroad and then they do not give us the 20% enriched fuel for our reactor, we are capable of producing it inside Iran."
NUCLEAR FUEL CYCLE
Mined uranium ore is purified and reconstituted into solid form known as yellowcake
Yellowcake is chemically processed and converted into Uranium Hexafluoride gas
Gas is fed through centrifuges, where its isotopes separate and process is repeated until uranium is enriched
Low-level enriched uranium is used for nuclear fuel
Highly enriched uranium can be used in nuclear weapons
In an initial reaction to Mr Ahmadinejad's comments, US state department spokesman P J Crowley said the US was "not prepared to change the deal. We are not interested in renegotiating it".
In a later response, a White House official told the BBC: "If Mr Ahmadinejad's comments reflect an updated Iranian position, we look forward to Iran informing the IAEA."
The official added: "If Iran has something new to say, we are prepared to listen."
BBC Tehran correspondent Jon Leyne, reporting from London, says that even now there will be scepticism over whether this Iranian change of heart really means anything.
The US is pressing hard for new sanctions against Iran because of the nuclear programme, so this could well just be a case of the Iranian government playing for time, trying to weaken forces lined up against it, he says.
In his interview, Mr Ahmadinejad also said there were ongoing negotiations about a possible prisoner swap for several Iranians jailed in the US for the three American hikers currently being held in Iran.
"There are some talks under way to have an exchange, if it is possible," he said. "We are hopeful that all prisoners will be released."
Mr Ahmadinejad did not mention any specifics, but in December Tehran released a list of 11 Iranians it says are being held in US prisons, including a nuclear scientist who disappeared in Saudi Arabia and a former defence ministry official who vanished in Turkey. The US has denied any knowledge of their whereabouts.
"I had said I would help in releasing them, but the attitude of some of the US officials damages the job," he said. "There are a large number of Iranians in prison in the US. They have abducted some of our citizens in other countries."
However, US National Security Council spokesman Mike Hammer told Agence France-Presse news agency: "We have not entered into any discussion with Iran about an exchange."
The three Americans - Shane Bauer, Sarah Shourd and Josh Fattal - were hiking in Iraq's northern Kurdistan region in July when they accidentally crossed the border, their families have said. Iranian prosecutors say they have been accused of spying.
Earlier, US Vice-President Joe Biden warned that Iran's leaders were "sowing the seeds of their own destruction" by suppressing the opposition protests that followed the disputed re-election of Mr Ahmadinejad in June.
"The people of Iran are thinking about, the very people marching, they're thinking about regime change," he told MSNBC.