Already facing UN sanctions over its sensitive nuclear program, Tehran announced recently it wanted to install "even more" than 3,000 centrifuges to enrich uranium at its Natanz underground facility.

"This would be a major miscalculation and mistake by the Iranian government," US Undersecretary of State Nicholas Burns said. "If Iran takes this step, it is going to confront universal international opposition.

"And if they think that they can get away with 3,000 centrifuges without another Security Council resolution and additional international pressure then they're very badly mistaken," Burns said.

In December, the UN Security Council passed 15-0 a resolution imposing sanctions on Iran for its repeated refusal to cooperate fully with the International Atomic Energy Agency (IAEA), the UN atomic energy watchdog, or to suspend uranium enrichment.

"They've already had China and Russia and all of the European countries and the United States oppose them. They've also had India and Egypt and Brazil oppose them a year ago at the IAEA Board of Governors," Burns said.

Another defiant move would "solidify the international opposition to Iran," he said, emphasizing again "it's a miscalculation."

An Iranian government spokesman said earlier this month that Iran would be making a major announcement on the "completion" of Iran's nuclear program during the 10-day anniversary celebrations for the Islamic revolution in February. He did not go into details.

The Islamic republic has so far declared the installation of two cascades of 164 centrifuges at the plant in Natanz and the installation of 3,000 centrifuges would mark a major step towards industrial enrichment.

The machinery is used to enrich uranium, a highly sensitive process that can be used both to make nuclear energy and a nuclear bomb.

It has so far shown no sign of caving into the Security Council resolution that imposed the first ever UN sanctions against Iran over its failure to suspend enrichment.

Iran, which insists that its nuclear program is entirely peaceful, this week banned 38 IAEA inspectors from working in the country.

It also sought removal of the official overseeing the IAEA's inspection of the Iranian nuclear program.

"It's outrageous," said State Department spokesman Sean McCormack. "They're inspector shopping."

He said that "the tone of those kinds of actions are indicative of their continued defiance.

"And this is not what the international system is looking for or, frankly, what it was hoping for in terms of Iranian behavior."

IAEA chief Mohamed ElBaradei is to report to the UN Security Council by February 21 on whether Iran has suspended enrichment.

If it has not, sanctions could be tightened and there is increased speculation that either the United States or Israel could eventually decide to bomb Iran in order to stop it from making nuclear weapons.

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