WASHINGTON (Reuters) - The United States has rebuffed pleas to join a European diplomatic drive to persuade Iran to give up any ambitions to add nuclear bombs to its arsenal, U.S. officials and foreign diplomats say.

For months, Britain, France and Germany have hoped to improve their bargaining power with the Islamic republic by involving Washington in a proposed accord over an end to its uranium enrichment activities.

That effort has intensified since President Bush´s re-election in November, culminating last week with ministerial visits to Condoleezza Rice days before she took up her new post as secretary of state, they said.

So far, the Americans show no sign of giving ground.

"It´s what they (the Europeans) have always wanted to do," a senior Bush administration official said. "(British Foreign Secretary) Jack (Straw) came over hoping Condi would change our policy and she didn´t."

A senior State Department official said Straw, who visited on Monday, one day before Germany´s Foreign Minister Joschka Fischer came on a similar mission, outlined European hopes for the negotiations.

The idea of getting the Bush administration into the talks "is in the air," he said.

"But we have not been (formally) asked yet and when we are, we will say, ´What good would it do?"´

The United States takes a harder line than the Europeans and wants Iran, which Bush grouped in an "axis of evil" with pre-war Iraq and North Korea, to be reported to the U.N. Security Council for possible international sanctions.

U.S. officials say that would increase pressure on Iran and push council members China and Russia to curtail arms and energy deals, respectively, which Washington believes could boost the Islamic republic´s nuclear capability.

Iran denies U.S. charges it is pursuing a nuclear bomb and says its programs are only for peaceful power generation needed to keep up with its growing population.

EURO LOBBYING COMES UP EMPTY

A European diplomat acknowledged the lobbying had failed to overcome U.S. skepticism about the talks, but Europe hoped Washington would eventually be persuaded if Iran kept to the agreement that offers energy, technology and trade incentives.

"The Europeans believe that the U.S. position will evolve in accordance with how Iran lives up to its commitments.

"But frankly there remains skepticism within the administration as to whether Iran is willing or capable of the transformation required," the diplomat said.

The Europeans -- with reluctant U.S. acquiescence -- have negotiated a freeze of Iran´s uranium enrichment in an accord similar to one that broke down last year. Enrichment, which Iran has refused to give up permanently, can help generate power or make bombs.

The head of the U.N. nuclear watchdog on Friday urged the United States to look to join the talks.

The United States has mixed tough talk with a few modest hints that diplomacy may yet work, but few analysts see any fundamental change in Bush administration policy.

"The administration is pleased with its policy and sees no reason to change," said Patrick Clawson, an Iran expert at the Washington Institute for Near East Policy, which has close ties to Iran´s arch- foe Israel.

The stance was a "gamble" that Iran´s hard-line rulers would be overthrown before they acquired a bomb, he said.

On Sunday, Rice told CBS´ Face the Nation: "We really do believe ... that this is something that can be dealt with diplomatically. What is needed is unity of purpose, unity of message to the Iranians, that we will not allow them to skirt their international obligations and develop nuclear weapons under cover of civilian nuclear power."

Her remarks came after the president refused to rule out a military strike and his hard-line vice president said Iran was top of the world´s trouble spots and warned the region´s biggest U.S. ally, Israel, could hit its facilities. (© Reuters 2005 01/30/05)