Obama seeks to calm 'drumbeat of war' over Iran

US President Barack Obama said on Tuesday the United States 'will not countenance' Iran developing a nuclear weapon but pledged to take a sober approach to dealing with Tehran's nuclear programme.

Obama said the announcement of six-power talks with Iran offered a diplomatic opportunity to defuse the crisis.

Amid mounting speculation that Iran's nuclear sites could be attacked in coming months, the president said that US politicians "beating the drums of war" had a responsibility to explain the costs and benefits of military action.

Earlier, US Defence Secretary Leon Panetta said the United States would take military action to prevent Iran from acquiring a nuclear weapon if diplomacy failed.

"Military action is the last alternative when all else fails," he told the annual policy conference of the biggest US pro-Israel lobbying group. "But make no mistake, when all else fails, we will act."

Six world powers have accepted an Iranian offer for talks on its disputed nuclear programme, the European Union's top diplomat said, after a year's standstill that has increased fears of a slide into a new Middle East war.

The announcement by EU foreign policy chief Catherine Ashton came shortly after Russia called for a resumption of face-to-face dialogue as soon as possible, saying an Iranian letter last month showed it was now ready for serious negotiations.

With Israel speaking increasingly loudly of resorting to military action, the talks could provide some respite in a crisis which has driven up oil prices and threatened to suck the United States into its third major war in a decade.

Iran's nuclear negotiator, Saeed Jalili, wrote to Ashton in February saying Tehran wanted to reopen negotiations and offering to bring unspecified "new initiatives" to the table.

"Today I have replied to Dr. Jalili's letter of Feb. 14," Ashton, speaking on behalf of the six powers after weeks of consultations with them, said in a statement. "I have offered to resume talks with Iran on the nuclear issue."

Ashton, who represents the United States, Russia, China, France, Britain and Germany in dealings with Iran, said the date and venue for the talks would now have to be agreed.

A senior EU official said these talks were not expected before the Iranian new year in two weeks, though there would be a series of preparatory meetings possibly in the coming days.

"Our overall goal remains a comprehensive negotiated, long-term solution which restores international confidence in the exclusively peaceful nature of Iran's nuclear programme, while respecting Iran's right to the peaceful use of nuclear energy," Ashton said in her reply to Jalili.

Western states are likely to tread cautiously, mindful of past accusations that Iran's willingness to talk has been a stalling tactic to blunt pressure and not a route to agreement.

The Islamic Republic's latest approach to the six powers comes at a time when it is suffering unprecedented economic pain from expanding oil and financial sanctions.