At a news conference with Germany's Foreign Minister Frank-Walter Steinmeier Rice said she could not verify "one way or another" the statement by Iranian President Mahmoud Ahmadinejad that his country had started to install 6,000 'ordinary' uranium enrichment centrifuges at its underground facility in Natanz.
She added that the U.S. made its conclusions on Iran relying on the information provided by the UN nuclear watchdog, the IAEA. According to the international organization, Iran currently uses around 3,000 'P-1' centrifuges, which are prone to breakdown when working at high speed for long periods.
Iranian authorities have repeatedly said the country needs 50,000 centrifuges to provide its annual requirements for nuclear fuel.
She also said that the U.S. is currently expecting Iran's reaction on the UN Security Council resolution, imposing additional sanctions on Iran, adopted in late February and expected to come into force when a 90-day deadline expires.
"We will always continue to consider refreshing both tracks but this is not the time, I think, to expect major changes," Rice told reporters. "We have just passed a Security Council resolution and we will see how Iran responds."
Steinmeier said that European nations were considering additional sanctions to be imposed on Iran.
Tehran has repeatedly rejected international demands to halt uranium enrichment, insisting it needs the process to generate electricity.
