Asked about a possible European proposal to include the United States in the sensitive negotiations, foreign ministry spokesman Hamid Reza Asefi said: "We would need to hear their arguments. We haven't seen any indication that American participation would help negotiations."

Asefi added that the European three of Britain, France and Germany leading current negotiations had not made such a suggestion.

He said comments by prominent MP Mahmoud Mohammadi challenging the United States to join negotiations were his "personal position and not the position of the Iranian government".

"The United States should either accept the results of the negotiations with the Europeans or otherwise, if they do not accept the position of their European allies, they should come to the negotiating table," Mohammadi said on Sunday.

Mohammadi, deputy head of parliament's national security foreign policy commission, said that "if the United States wishes to assure itself of the peaceful nature of our nuclear activities, their participation in the negotiations can be examined."

Iran and the United States broke off diplomatic relations shortly after Iran's Islamic revolution in 1979. The two sides remain fiercely at odds, with the US accusing Iran of seeking to acquire nuclear weapons under the guise of an atomic energy programme.

In return for "objective guarantees" that Iran will not develop the bomb, the so-called EU-3 are offering a package of incentives.

The United States has given its backing to the European effort after earlier pushing to take the matter before the United Nations for possible sanctions, but has also not ruled out using force.

Talks remain deadlocked over Iran's insistence that it maintain the right to enrich its own nuclear fuel. There are widespread fears that the technology could be diverted to produce highly enriched uranium for a nuclear bomb.

The EU is currently considering, ahead of a meeting next week with Iranian negotiators in Geneva, a proposal by Tehran to allow it to produce enriched uranium on a small scale.

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