Iran reveals new atomic work, draws Western rebuke

Diplomats in Vienna said last week that Iran was installing advanced enrichment centrifuges at the underground Natanz facility, accelerating activity that could give Tehran the means to make atom bombs in the future if it chose to.

Ahmadinejad said a machine with greater capacity was tested at Natanz on Tuesday: "The capacity of these new machines ... is five times greater than the current machines." A senior official said the president was referring to the advanced centrifuges.

Centrifuges are machines that can spin compounds of uranium at supersonic speed to separate out and concentrate the most radioactive isotope of the element.

Nuclear analysts say around 1,500 such machines would be needed for Iran to manufacture the minimum amount of highly enriched uranium needed for one crude warhead.

The five permanent members of the U.N. Security Council and Germany plan to meet in Shanghai on April 16 to discuss whether to sweeten their 2006 offer of incentives to persuade Iran to curb its nuclear program, a Western diplomat told Reuters.

Iran has ruled out halting or limiting its nuclear work in exchange for trade and other incentives, and says it will only negotiate with the U.N. nuclear watchdog.

France said major powers may need to tighten U.N. sanctions against Iran if it continues to ignore their demands.

"I fear that we will have to continue on the path of sanctions if we do not receive a response from the Iranians," French Foreign Minister Bernard Kouchner said in Paris.

(Additional reporting by Zahra Hosseinian, Hashem Kalantari and Fredrik Dahl in Tehran, Francois Murphy in Paris, Adrian Croft in London, Karin Strohecker in Vienna, Oleg Shchedrov in Moscow, Louis Charbonneau at the U.N. and by Washington bureau; Writing by Parisa Hafezi; Editing by Richard Williams)