Iranian President Mahmoud Ahmadinejad speaks at a ceremony in Iran's nuclear enrichment facility in Natanz, 186 miles south of capital city Tehran, Iran. Iran announced Monday that it has begun enriching uranium with 3,000 centrifuges, a dramatic expansion of a nuclear program that has drawn U.N. sanctions and condemnation from the West.

Iranian President Mahmoud Ahmadinejad said Monday that his country had begun producing nuclear fuel on an industrial scale, an accomplishment that, if verified, would significantly advance Iran’s nuclear program.

But U.S. and British officials, along with international nuclear experts, cast doubt on the announcement, noting that the Iranians did not offer evidence to support the assertion and suggesting privately that the remarks were tailored toward generating national pride in a program that the U.N. Security Council has ordered Iran to suspend.

“With great pride I announce, as of today, our dear country Iran is among the countries of the world that produces an industrial level of nuclear fuel,” Ahmadinejad said in a nationally televised speech from the town of Natanz, site of Iran’s enrichment facility.

Iran’s top nuclear negotiator, Ali Larijani, seemed to confirm separately to reporters that scientists had begun enriching uranium through a cascade of 3,000 centrifuges. Larijani did not elaborate, and Iranian officials offered no photographs or video showing a new cascade at work. In the past, they have taken journalists and foreign diplomats on tours to witness advancements in the program, which Iran says is part of an effort to develop nuclear energy, not weapons.

U.N. inspectors from the International Atomic Energy Agency reported in March that Iran was operating two smaller test cascades of 164 centrifuges each and trying to build more. But inspectors who visited Iran several weeks ago did not witness an operating cascade of the size Larijani suggested, and they are expected to return to Iran in coming days, according to a senior European diplomat familiar with the inspectors’ mission.

Iranian officials said a year ago that they intended to build a 3,000-centrifuge cascade for uranium enrichment by this spring. But beset by technical difficulties, they have repeatedly missed publicly set goals, according to U.N. inspectors and nuclear experts in the U.S. and British governments.

Uranium enriched to low levels, such as 5 percent, can produce fuel for a nuclear reactor. So far, the Iranians have stuck with low levels during research with small cascades. But the material becomes bomb-grade when enriched to 90 percent or higher, a process made easier with a large number of cascades spinning together in unison.

The Bush administration has asserted that Iran is using its energy program as a cover for a weapons program and wants it stopped.

In December, the U.N. Security Council began to impose a string of mild financial restrictions on the Tehran government and has threatened additional measures if Iran does not halt its work by 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,” State Department spokesman Sean McCormack said.