VIENNA, Nov 24: In a dramatic 11th hour move before a crucial UN atomic agency meeting, Iran on Wednesday asked the watchdog to exempt several dozen centrifuges from its pledge to freeze its nuclear fuel cycle.

The development was rejected by the European Union, which earlier this month negotiated what was supposed to be a halt in all of Iran's uranium enrichment activities.

It comes before a meeting on Thursday of the International Atomic Energy Agency (IAEA) which will decide whether to bring Iran before the UN Security Council for possible sanctions, sought by the United States for what it says is a covert nuclear weapons program.

A diplomat close to the agency said the Iranians "are trying to convince the IAEA to leave several dozen of the centrifuges unsealed for RD (research and development) purposes in addition to other equipment which has direct use for enrichment".

A Western diplomat said it would be "outrageous" if Iran at the last minute exempted some centrifuges, the machines used in enriching uranium. "It is not acceptable to us," a European diplomat said.

Under the terms of a deal hammered out with Britain, France and Germany, Tehran was to suspend all uranium enrichment activities from Monday, a move which is now being verified by the IAEA.

Iran had continued to produce the uranium gas that is the feedstuff for enriching uranium only days before Monday's ban, in a move which one European diplomat characterized as "not very helpful" as it led to doubts about Iran's intentions and the future of the suspension deal.

Enriched uranium, made by spinning uranium gas in what can be cascades of thousands of centrifuges, can serve as fuel for nuclear reactors or as the raw explosive material for atomic bombs.

Iran has moved quickly to "sanitize" a site in northeastern Tehran alleged to be at the heart of its feared pursuit of nuclear weapons, an Iranian opposition group alleged on Wednesday.

Speaking in London, National Council of Resistance (NCRI) member Farid Soleimani, who alleged nine days ago in Vienna that secret enrichment work was being done at the Centre for Development of Advance Defence Technology, said the top secret site now has been sealed off.

PRAGMATISM: Diplomats said Washington had taken a pragmatic decision to support the European draft, even though it falls short of demanding possible UN sanctions against Iran.