The newspaper said the assertion involves Iran's claim that even while it begins to enrich small amounts of uranium, it is pursuing a far more sophisticated way of making atomic fuel.

Western analysts long suspected that Iran had a second, secret program -- based on the P-2 centrifuge provided by the renegade Pakistani nuclear engineer Abdul Qadeer Khan -- separate from the activity at its main nuclear facility at Natanz, the report said. But they had no proof.

Then on Thursday, President Mahmoud Ahmadinejad said that Tehran was "presently conducting research" on the P-2 centrifuge, boasting that it would quadruple Iran's enrichment powers.

European diplomats said a delegation of Iranian officials is due to arrive on Tuesday in Vienna, where the International Atomic Energy Agency will press them to address the new enrichment claim, as well as other questions about Iran's program, including a crude bomb design found in the country, The Times said.

"This is a much better machine," the paper quotes an unnamed European diplomat as saying of the advanced centrifuge, which was a centerpiece of Pakistan's efforts to build its nuclear weapons and was found in 2004 in Libya, when that country gave up its nuclear program.

The diplomat added that the Iranians will now have to explain whether Ahmadinejad was right, and if so, whether they recently restarted the abandoned program or have been pursuing it in secret for years, the paper said.

If Iran moved beyond research and actually began running the machines, it could force American intelligence agencies to revise their estimates of how long it would take for Iran to build an atom bomb -- an event they now put somewhere between 2010 and 2015, according to the report.

Robert Joseph, the under secretary of state for arms control and international security, said in an interview on Saturday that President Ahmadinejad's claim constituted "the first time I've ever heard the Iranians admit" to have a significant effort on the advanced technology, The Times pointed out.

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