"Our concern is the development of weapons from nuclear power and proliferation," Domenici, a Republican who is chairman of the Senate's committee on energy and natural resources, told AFP in Vienna.

He said the problem with Iran was "what assurance are they willing to give, what protocol are they willing to follow ... so as to assure the world that it (their nuclear program) will be peaceful."

Domenici spoke after meeting with International Atomic Energy Agency chief Mohamed ElBaradei, whose agency has been investigating US charges that the Islamic republic is secretly developing nuclear weapons.

The IAEA called on Iran earlier this month to resume a full suspension of nuclear fuel activities it had undertaken as a confidence-building measure for talks with the European Union on guaranteeing its atomic program was peaceful.

Washington was not part of the EU diplomatic initiative, but supported it.

The IAEA is to report September 3 on Iranian compliance, with the EU ready to take Teheran before the UN Security Council for possible sanctions if the suspension is not resumed.

Iran suspended nuclear activities last November but broke that suspension earlier this month as it rejected an EU offer of trade and other benefits, saying they failed to recognize the Islamic republic's rights under the nuclear Non-Proliferation Treaty (NPT) to make nuclear fuel.

Fuel in the form of enriched uranium, or plutonium, can power civilian reactors but in highly refined form can also be the raw material for atomic bombs.

Domenici drew a clear distinction however between Washington's pressure on Teheran and support for nuclear power worldwide.

"I am not suggesting that in any way there should an American or any other lock on nuclear power. Every country should have an opportunity including developing countries to have civilian nuclear power.

"We're not part of any move that is trying to prevent that. America supports nuclear power," the US senator said.

The United States nonetheless fears that making nuclear fuel would give Iran a so-called breakout capacity to make atomic weapons.

Domenici said Iran's intentions were suspect given that an IAEA investigation found that Teheran had been developing nuclear technology in secret for about 18 years.

The US senator, a congressional leader in non-proliferation matters, said that if Iran had nothing to hide it should cooperate fully with the international agency.

Domenici rejected the argument that US research into bunker buster weapons or expansion of its own enrichment capacity could be taken by Iran as excuses to continue with an Iranian program.

He said studies into bunker buster weapons were not about how "to build any weapons but rather to research the project and potential for a weapon that would have much more of a capacity to penetrate before it explodes."

"There's no new nuclear warhead," Domenic stressed, adding that "the delivery system for penetration that is being studied is not nuclear."

As for a new uranium enrichment facility for which licensing is being worked out in Domenici's home state New Mexico, the senator said that it would be for low enriched uranium, which is not used to produce weapons.

The United States "building or desiring to have an additional enriched uranium plant is also not for something new but rather for something old," since the United States gets 20 percent of its electricity from nuclear power and needs to make more fuel.

"We used to be the world's single biggest supplier. We're a big importer now so the time has come to add to the world's supply," Domenici said.

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