The top US military officer warned on Monday that any strike against Iran would not be "decisive" in countering Tehran's nuclear program.

Admiral Mike Mullen, the chairman of the US Joint Chiefs of Staff, said he supported using diplomatic and economic pressure against Iran and repeated his view that military action could carry "unintended consequences."

"No strike, however effective, will be in and of itself decisive," Mullen told a press conference after recently returning from a visit to the Middle East.

But he said the US military stood ready with plans for possible action if necessary.

"Let me be clear: We owe the (defense) secretary and the president a range of options for this threat. We owe the American people our readiness."

Mullen's comments came as the United States pushed for fresh sanctions against Iran over its nuclear program and before Israeli Defense Minister Ehud Barak visits Washington this week.

The admiral said he believed Iran was "on a path to achieve nuclear weaponization" and that the effort "further destabilizes the region."

He said there was widespread concern in the Middle East about Iran's role and its nuclear ambitions.

He said that "it isn't just a nuclear capable Iranian military our friends worry about, it's an Iran with hegemonic ambitions and a desire to dominate its neighbors."

Mullen and other top US officials have said previously military action against Iran cannot be ruled out.

"But, as I have said many times, I worry a lot about the unintended consequences of any sort of military action.

"For now, the diplomatic and the economic levers of international power are and ought to be, the levers first pulled," Mullen said.

Iran meanwhile said on Monday it is considering plans to build two new uranium enrichment plants concealed inside mountains to avert possible air strikes.

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.

Iran's atomic chief Ali Akbar 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."

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.

Mullen returned last week from a trip to Egypt, Israel, Jordan, Saudi Arabia and the United Arab Emirates.