VIENNA, Austria - Iran has manufactured about 4,000 centrifuges capable of enriching uranium to weapons grade, an exiled Iranian dissident who helped uncover nearly two decades of covert nuclear activity in 2002 said today.

Alireza Jafarzadeh told The Associated Press the centrifuges - which he said are unknown to the U.N. nuclear watchdog agency - are ready to be installed at Iran's nuclear facility in Natanz.

Jafarzadeh, who runs Strategic Policy Consulting, a Washington-based think tank focusing on Iran and Iraq, said the information - which he described as "very recent" - came from sources within the Tehran regime who have proven accurate in the past.

None of Jafarzadeh's claims could be independently verified.

The Vienna-based International Atomic Energy Agency, which was convening an emergency meeting on Iran later today, did not comment on the centrifuge allegations. The agency previously had said it was aware of the existence of 164 centrifuges at Natanz, 300 miles south of Tehran.

Iran also did not immediately comment on Jafarzadeh's claims.

Under an agreement with the IAEA, Iran had pledged to stop building centrifuges, which can be used to enrich uranium to levels high enough to fuel a nuclear weapon.

Centrifuges also can be used for the peaceful generation of nuclear energy, which Iran insists is its only intention. The United States contends the country is running a covert effort to produce nuclear weapons.

"These 4,000 centrifuge machines have not been declared to the IAEA, and the regime has kept the production of these machines hidden from the inspectors while the negotiations with the European Union have been going on over the past 21 months," Jafarzadeh said.

Iran on Saturday rejected a package of EU incentives and on Monday, it announced it had resumed uranium conversion activities at its nuclear facility at Isfahan.