Israeli officials have expressed doubt over claims by Iranian President Mahmoud Ahmadinejad on Saturday that his country now possesses 6,000 centrifuges. Ahmadinejad's announcement, reported by a semi-official news agency, is a significant increase in the number of uranium-enriching machines in Teheran's nuclear program. It also comes a week after the US reversed course in negotiations over Iran's nuclear program by sending a top American diplomat to participate in talks between Teheran and world powers. But an Israeli official who closely monitors the Iranian nuclear program told The Jerusalem Post that Ahmadinejad was probably lying. "Our assessment, based on the latest available information and recent reports from the International Atomic Energy Agency, is that the figure of 6,000 centrifuges is unlikely," the official said. "We believe a figure of between 3,400 and 3,500 is more accurate." Ahmadinejad asserted Saturday that Iran's interlocutors had agreed to allow it to continue to run its program as long as it was not expanded beyond 6,000 centrifuges, state radio reported. "Today, they have consented that the existing 5,000 or 6,000 centrifuges not be increased and that operation of this number of centrifuges is not a problem," state radio quoted Ahmadinejad as saying. International negotiators are trying to persuade Teheran to agree to a compromise under which Iran would agree to temporarily stop expansion of enrichment activities. "Announcements like this, whatever the true number is, are not productive and will only serve to further isolate Iran from the international community," said White House spokesman Carlton Carroll. Iran declared in April that it was aiming to double the 3,000 centrifuges it was running in its underground uranium enrichment plant in Natanz. "Islamic Iran today possesses 6,000 centrifuges," the semi-official Fars news agency quoted Ahmadinejad as saying Saturday in an address to university professors in the northeastern city of Mashhad. The Israeli official explained that by exaggerating the numbers, the Iranian president hopes to achieve two goals. First, he exerts pressure on his own nuclear technicians to step up the pace of their work aimed at producing enough fissile material to make a bomb. Second, Ahmadinejad seeks conflict with the West so he can portray himself as the defender of Iranian national interests in the run-up to next year's presidential elections. Ahmadinejad has failed to deliver on promises of improving the economy and creating jobs, and the nuclear issue remains his only hope of drumming up much needed domestic political support. "Ultimately it is not president Ahmadinejad who decides Iran's nuclear policy but the country's spiritual leader Ali Khamenei," the Israeli official explained. "Ahmadinejad will not compromise because he seeks confrontation, but Khamenei or another presidential candidate may be tempted to accept a compromise package drawn up by the West in return for halting uranium enrichment." The July 19 talks in Geneva were aimed at trying to reach a deal with Iran, and in exchange, the six world powers - the US, Germany, Britain, France, Russia and China - would hold off on adopting new UN sanctions against Iran. But participants at Geneva said Iranian negotiators skirted the freeze issue despite the presence of US Undersecretary of State William Burns. Secretary of State Condoleezza Rice later accused Iran of not being serious at the Geneva talks. She warned that all six nations were serious about a two-week deadline for Iran to agree to freeze suspect activities and start negotiations or else be hit with a fourth set of UN penalties. On Saturday, Iran's chief delegate to the IAEA, Ali Ashgar Soltanieh, lashed back at American criticism of his country's role in the Geneva talks. His US counterpart, Gregory L. Schulte, told Britain's Daily Telegraph in an interview published earlier this week that Teheran's chief negotiator delivered a "rambling" discourse in Geneva instead of focusing on the talks. Soltanieh told The Associated Press on Saturday that Schulte's comments "further damage his credibility and that of his country." He described the Geneva talks as "successful and constructive." A report by the UN's nuclear monitoring agency that was delivered to the UN Security Council in May said Iran had 3,500 centrifuges, though a senior UN official said at the time that Iran's goal of 6,000 machines running by the summer was "pretty much plausible." In the enrichment process, uranium gas is pumped into a series of centrifuges called "cascades." The gas is spun at supersonic speeds to remove impurities. Enriching at a low level produces nuclear fuel, but at a higher level it can produce the material for a warhead. The workhorse of Iran's enrichment program is the P-1 centrifuge, which is run in cascades of 164 machines. But Iranian officials confirmed in February they had started using the IR-2 centrifuge that can churn out enriched uranium at more than double the rate. A total of 3,000 centrifuges is the commonly accepted figure for a nuclear enrichment program that is past the experimental stage and can be used as a platform for a full industrial-scale program that could churn out enough enriched material for dozens of nuclear weapons. Iran says it plans to move toward large-scale uranium enrichment that ultimately will involve 54,000 centrifuges. Ahmadinejad called the US participation in the latest round of nuclear talks "a victory for Iran." In the past, the US said it would join talks only if Iran suspends uranium enrichment first. "The presence of a US representative... was a victory for Iran, irrespective of the outcome... The US condition was for Iran to suspend enrichment but they attended [the talks] without such a condition being met," Ahmadinejad was quoted as saying in the state radio report. On Wednesday, Ahmadinejad praised the US participation at the talks as a step toward recognizing Teheran's right to acquire nuclear technology.