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. Washington said it was skeptical of the alleged progress and any of its allegations would be viewed with caution. “Iran has in the past, you know, announced that it is - it was running a certain number of centrifuges that didn't really pan out with regard to the IAEA's (International Atomic Energy Agency's) own estimate. “So it's not clear,” he said. President Mahmoud Ahmadinejad 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 the number was 6,000. A diplomat close to the UN's nuclear watchdog, the 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. 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.” State Department spokesman Robert Wood said : “We want to engage Iran and we ... have said so very clearly and publicly, and so we wait for Iran to reciprocate.” China 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. Foreign nuclear analysts believe Tehran has yet to prove it has mastered industrial-scale enrichment of uranium. The US, 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.