WASHINGTON - SIX world powers seeking to persuade Teheran to rein in its nuclear program have yet to receive a formal reply from Iran on their proposal to resume long-stalled talks, US officials said on Wednesday.

EU foreign policy chief Catherine Ashton, who represents world powers in the nuclear dialogue with Iran, has proposed to resume the long-stalled talks in Vienna, starting with a dinner meeting on Nov 15, followed by two days of consultations.

Top Iranian officials, including Minister Manouchehr Mottaki and top nuclear negotiator Saeed Jalili, welcomed the offer but have yet to present a formal response. And President Mahmoud Ahmadinejad has said negotiations were the only solution.

'The first thing we're waiting for is a response from Iran,' State Department spokesman PJ Crowley said. He said the so-called P5+1 that groups the United States, Britain, China, France, Germany and Russia was prepared to discuss nuclear fuel swap proposals with the Islamic republic 'if Iran is prepared to sit down and seriously debate.'

'But at the same time, we need to have Iran come forward and demonstrate affirmatively that it's living up to its obligations, and its nuclear program is for peaceful purposes,' he added.

Should they take place as planned, the talks would be the first high-level meetings between Iran and the P5+1 since another round held Oct 1, 2009 in Geneva.

World powers still waiting