| ISFAHAN, Iran
ISFAHAN, Iran Iran announced further progress in its disputed nuclear program on Thursday, a day after world powers said they would invite Tehran to direct talks, but the declaration met some Western skepticism.
President Mahmoud Ahmadinejad, saying Tehran was ready for negotiations if they were based on respect and justice, said Iran had mastered the nuclear fuel cycle and it had also tested new, more advanced machines for enriching uranium.
Speaking at the same televised event to mark Iran's National Nuclear Day, the head of Iran's Atomic Energy Organization, Gholomreza Aghazadeh, said it was now running 7,000 enrichment centrifuges. In February, Iran had said the number was 6,000.
Western analysts say Iran has in the past exaggerated progress to boost its bargaining position with major powers and a U.S. State Department spokesman referred to this practice.
"I think we certainly could view it with skepticism," spokesman Robert Wood said of Iran's latest announcement.
A diplomat close to the U.N.'s nuclear watchdog, the International Atomic Energy Agency (IAEA), also questioned the extent of new Iranian advances.
"It doesn't appear that there has been any dramatic change in the progress of the program, except for some additional centrifuges being put in place," said the diplomat, making a comparison to the last IAEA report in February.
The United States and its Western allies suspect Iran's nuclear work is aimed at building bombs and wants it to stop enrichment activity, which can have both civilian and military uses. Iran denies the charge and rules out any halt.
Washington reacted cautiously to Ahmadinejad's comments on Iran's readiness for negotiations if they were "based on justice and complete respect for rights and regulations."
Breaking with past U.S. policy of shunning direct talks with Tehran, U.S. President Barack Obama's administration this week said it would join nuclear discussions with Iran from now on.
State Department spokesman Wood said in Washington: "We want to engage Iran and we ... have said so very clearly and publicly, and so we wait for Iran to reciprocate."
China, a veto-wielding member of the U.N. Security Council and a close energy and trade partner with Iran, said it welcomed signs of renewed engagement and urged Tehran and other powers to pursue contacts aimed at defusing the long-running row.
Underlining Iran's determination to press ahead with its nuclear drive, Ahmadinejad inaugurated the nation's first atomic fuel fabrication plant near the central city of Isfahan.
Officials said it would produce uranium pellets, fuel rods and fuel to power the Arak heavy water reactor.
"I sincerely congratulate the Iranian nation ... for the great success ... in completing the fuel management cycle," Ahmadinejad said.
The nuclear fuel cycle includes mining of uranium ore, uranium enrichment, fabrication and use of nuclear fuel, reprocessing of used fuel, and disposal of radioactive waste.
In its February report, the IAEA said it could not verify Iran's planned Arak heavy water reactor was being designed only for peaceful uses because Tehran had been denying visits by IAEA inspectors since August.
Ahmadinejad also said Iran had tested two new types of uranium enrichment centrifuges with a capacity "a few times higher than the existing centrifuges" currently in use.
Up to now, Iran has been enriching with only a fragile, inefficient 1970s vintage machine known as the P-1, adapted from a model obtained from former Pakistani-run nuclear smugglers.
"The Iranian nation ... is a nation that would achieve what it wants despite enmities and enemies," Ahmadinejad said.
Foreign nuclear analysts believe Tehran has yet to prove it has mastered industrial-scale enrichment of uranium, the key to making fuel in large, usable quantities and the most technically difficult aspect of producing nuclear power.
The United States, Russia, China, France, Germany and Britain said on Wednesday they would ask European Union foreign policy chief Javier Solana to invite Tehran to a meeting to find "a diplomatic solution to this critical issue."
Despite reaching out to Tehran, analysts and diplomats say the Obama administration would be realistic about its chances of a breakthrough and was aware that Iran may use talks to buy time to complete its nuclear program.