Last month, Brazil and Turkey resurrected parts of the proposal, under which Iran would ship 1.2 tonnes of its low-enriched uranium stockpile abroad in return for the fuel, seen as a way to reduce tensions with the West.
|Iran has vowed it will continue its nuclear programme despite growing pressure [AFP]
But the new IAEA report said Iran's low-enriched uranium stockpile had grown to 2.4 tonnes, so that even if the 1.2 tonnes was shipped out now, it would still leave Iran enough material for a nuclear weapon if enriched to higher levels.
Iran says its nuclear work is for peaceful uses only.
But major world powers have recently backed a draft UN resolution that would authorise a fourth round of sanctions against its nuclear work.
"Based on this report Washington is going to feel justified in downplaying the Brazilian-Turkish-Iranian deal and focusing on sanctions instead," said David Albright, the head of the Institute for Science and International Security.
Iran's raising of the enrichment level to 20 per cent has heightened Western suspicions because it takes the material closer to the 90 per cent purity needed to make atomic weapons.
The country is also thought to lack the capability to make the special fuel assemblies needed for the medical research reactor.
No swap deal
Meanwhile on Monday, the Iranian ambassador to Iraq said the recent release of two Iranians captured by US forces in Iraq was not an indication of any impending deal to free three Americans held by Tehran on spying charges.
Hassan Kazemi Qomi told the Associated Press news agency that the fate of the Americans, who have been held since July, is in the hands of the Iranian judiciary and has no connection to the release of two Iranians earlier this month.
"There were no deals. They are in the custody of the judiciary system.''
The detained Americans - Sarah Shourd, Shane Bauer and Josh Fattal - were arrested along the Iraqi border and accused of being spies.
Their families say they were hiking in northern Iraq's mountainous Kurdish region and if they strayed into Iran, it was unintentional.