Iran said on Monday it is considering plans to build two new uranium enrichment plants concealed inside mountains to avert air strikes, drawing condemnation from the United States.

The announcement from Iran's atomic chief Ali Akbar Salehi came soon after top US General David Petraeus warned that Washington would now pursue a "pressure track" against Iran to thwart its galloping nuclear programme.

"Inshallah (God willing), in the next Iranian year (starting in March) as ordered by the president we may start the construction of two new enrichment sites," Salehi told ISNA news agency.

Last November, President Mahmoud Ahmadinejad announced Iran would build 10 new uranium enrichment plants, after Tehran was strongly rebuked by world powers for building a second enrichment plant near the Shiite holy city of Qom.

Salehi said the enrichment capacities of the new sites would be similar to the existing facility in the central city of Natanz, where a defiant Tehran is refining uranium despite three sets of UN sanctions.

According to the latest UN nuclear watchdog report, Iran has installed in Natanz 8,610 centrifuges, the device which rotates at supersonic speed to enrich uranium.

Of these, 3,772 centrifuges are actively enriching uranium under the supervision of the International Atomic Energy Agency (IAEA).

Salehi said the new plants will be equipped with new generation centrifuges and the facilities would be hidden in mountains so as to protect them from "any attacks."

The United States said the move showed Iran rejected diplomatic engagement with the international community.

"This is further evidence that Iran refuses to engage cooperatively and constructively with the IAEA," State Department spokesman Philip Crowley told reporters.

The top US military officer said that any military strike against Iran would not be "decisive" in countering its nuclear programme.

"No strike, however effective, will be in and of itself decisive," Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, told a news conference, adding that he supported using diplomatic and economic pressure against Iran.

Elsewhere on the diplomatic front, European nations meeting in Brussels appeared divided over boosting sanctions against Iran.

"Unhappily all the actions by the Iranian side for weeks confirm that we must move to (more) sanctions," French European Affairs Minister Pierre Lellouche said.

But several of his EU counterparts said diplomacy had not run its course and insisted on the need for a UN Security Council decision.

On Sunday, Petraeus said the United States, which along with its ally Israel has not ruled out military strikes against Iran's nuclear sites, would increase pressure on Tehran.

"I think that no one at the end of this time can say that the United States and the rest of the world have not given Iran every opportunity to resolve the issues diplomatically," said Petraeus, head of US Central Command.

"That puts us in a solid foundation now to go on what is termed the pressure track. That's the course on which we are embarked now," he told NBC television.

Israeli Prime Minister Benjamin Netanyahu on Monday insisted "now" was the time for new sanctions on Iran's oil exports.

World powers suspect Iran is enriching uranium to make nuclear weapons, a charge Tehran denies.

Enriched uranium can be used as fuel to power nuclear reactors or in highly refined form to produce the fissile core of an atom bomb.

Iran is at loggerheads with world powers for not accepting an IAEA-drafted deal which would supply it with nuclear fuel for a Tehran research reactor in return for the transfer of the bulk of its low-enriched uranium.

Tehran insists it wants a simultaneous exchange of the two materials, with the transfer taking place inside the country, a demand strongly opposed by world powers.

Tensions rose further after Iran began work on enriching uranium to 20 percent purity from 3.5 percent, which according to experts brings it closer to the 93 percent level required for making a bomb.

Turkish Prime Minister Recep Tayyip Erdogan, meanwhile, warned in a newspaper interview that a pre-emptive Israeli strike on Iran's nuclear facilities would be a "disaster of unpredictable consequences."

"We have to find a solution through diplomatic means," he told the leading Spanish daily El Pais. "We must not leave the negotiating table."

burs/srm