Iranian students chant slogans during a gathering on “National Day of the Nuclear Technology,” in Tehran. AP photo

NATANZ, Iran - Iran announced today it has begun enriching uranium with 3,000 centrifuges, defiantly expanding a nuclear program that has drawn U.N. sanctions and condemnation from the West.

Iranian President Mahmoud Ahmadinejad said at a ceremony at the enrichment facility at Natanz that Iran now is capable of enriching nuclear fuel “on an industrial scale.”

Asked if Iran has begun injecting uranium gas into 3,000 centrifuges for enrichment, top nuclear negotiator Ali Larijani replied, “Yes.” He did not elaborate, but it was the first confirmation that Iran had installed the larger set of centrifuges after months of saying it intends to do so. Until now, Iran was only known to have 328 centrifuges operating.

Uranium enrichment can produce fuel for a nuclear reactor or the material for a nuclear warhead. The United States and its allies accuse Iran of intending to produce weapons, a charge the country denies.

Sean McCormack, the State Department spokesman, said the U.N. Security Council and the U.N. nuclear watchdog group “don't believe Iran's assurances that their (nuclear) program is peaceful in nature.”

The Vienna-based International Atomic Energy Agency, the U.N. nuclear watchdog, had no immediate comment on Monday's announcement.

The United Nations has vowed to ratchet up sanctions as long as Iran refuses to suspend enrichment. The Security Council first imposed limited sanctions in December, then increased them slightly last month and has set a new deadline of late May.

“What we are looking for are reasonable Iranian leaders who view the cost-benefit calculation and see that it is not to the benefit of the Iranian people to continue to pursue the course on which they find themselves,” McCormack said.

Iranian state television reported Monday that an Iranian Revolutionary Guard general who is under travel restrictions urged by the sanctions has visited Russia without any difficulty.

Gen. Mohammad Baqer Zolqadr, who is also deputy interior minister for security affairs, was quoted on the state TV Web site as saying that his six-day journey to Moscow, which ended Monday, showed “the ineffectiveness of the resolution.”

The resolution urges all governments to ban visits by the 15 individuals and says that should such visits occur - presumably for exceptional circumstances - the countries should notify a U.N. committee.

Tensions are also high between Iran and the West following the 13-day detention of 15 British sailors by Iran. The sailors, who were seized by revolutionary guards off the Iraqi coast, were released on Wednesday, but since then have said they were put under psychological pressure by their captors to force them to “confess” to being in Iranian waters when captured, angering many in Britain.

In his speech, Ahmadinejad insisted Iran has been cooperative with the U.N. nuclear watchdog, allowing it inspections of its facilities.

“With great honor, I declare that as of today our dear country has joined the nuclear club of nations and can produce nuclear fuel on an industrial scale,” Ahmadinejad said.

Larijani, said his country was willing to offer assurances that its program is peaceful. But he said the West must accept its nuclear program as a fact.

Today, Iran announced it had first enriched uranium using an array of 164 centrifuges.

Across Iran, school bells rang on Monday to mark the “national day of nuclear energy.” The government sent out text messages of congratulations for the occasion to millions of mobile phone users.

In Tehran, some 200 students formed a human chain at Iran's Atomic Energy Organization while chanting “death to America” and “death to Britain.” The students burnt flags of the U.S. and Britain.