Number of centrifuges increases

Iran has increased the number of operating centrifuges at its uranium enrichment plant to 4,000, a top official said, pushing ahead with the nuclear program despite threats of new U.N. sanctions.

The number was up from the 3,000 centrifuges that Iran announced in November that it was operating at its plant in the central city of Natanz. Still, it is well below the 6,000 it said last year that it would operate by this summer, suggesting the program may be behind schedule.

Deputy Foreign Minister Ali Reza Sheik Attar, who visited Natanz last week, said Iran was preparing to install even more centrifuges. He did not offer a time frame.

The U.N. has imposed three rounds of sanctions on Iran for its refusal to freeze its enrichment program, which can be used to produce fuel for a nuclear reactor or the material needed for a nuclear warhead.