Iran has asked the UN nuclear watchdog to exempt several dozen centrifuges from a freeze on its sensitive atomic projects, but European Union negotiators rejected the request, diplomats said on Wednesday.

A diplomat close to the International Atomic Energy Agency (IAEA) said Iran is "trying to convince the IAEA to leave several dozen of the centrifuges unsealed for research and development purposes."

Another diplomat said Iran's request is equal to a "chutzpah" before the IAEA convenes Thursday to determine whether Iran is fulfilling its commitment to stop all uranium enrichment and related activities, and considers possible sanctions if it isn't.

A Western diplomat believed the request is a clear message that Teheran has no intention of ending its nuclear fuel production.

A diplomat revealed on condition of anonymity that EU negotiators have rejected Iran's request.

After lengthy negotiations with France, Germany and Britain, Iran said last week it would stop all uranium enrichment-related activities in exchange for nuclear technology from Europe.

The United States has accused Iran of secretly developing nuclear weapons, a charge strongly denied by Tehran, which said its nuclear plan was completely for peaceful purposes.