Among the most important was President Mahmoud Ahmadinejad's boast that the country was researching a new generation of advanced centrifuges for uranium enrichment.

But he said there had been longstanding concern that Iran was developing the more advanced centrifuge.

It is the most advanced centrifuge sold by Dr. Khan's network.

But the advanced centrifuges never reached Libya.

In addition, they said they had received 4,000 more advanced centrifuges, P-2's, which were kept out of sight.

Agency experts became convinced that the Iranians must have received the same designs for an advanced centrifuge, known as the P2, that the Libyans had.

It plans to develop more advanced centrifuges so it can enrich more quickly.

The tubes are the heart of Urenco's advanced uranium-enriching centrifuges.

In April, Iran disclosed that it was trying to build more advanced and powerful centrifuges known as model P-2, which would speed its enrichment program.

The P-2, a second-generation Pakistani model, was the most advanced centrifuge sold by Dr. Khan's network.