The request for additional US concessions is viewed as another sign the talks between Iran and the Europeans have made little headway since the two sides renewed efforts to reach agreement last autumn.

A US official said the request for incentives was vague. Several European governments have argued that successful negotiations with Iran hinge heavily on greater US involvement in the talks, including an offer to normalize relations with the Islamic republic and an assurance the United States will not attack Teheran.

Tensions over Iran's nuclear ambitions, already heightened by recent threats and accusations, spiked further Tuesday when Iran's foreign minister, Kamal Kharrazi, said his country is determined to pursue the production of nuclear energy, but not atomic weapons.

``Iran, for its part, is determined to pursue all legal areas of nuclear technology, including enrichment, exclusively for peaceful purposes, and has been eager to offer assurances and guarantees that they remain permanently peaceful,'' Kharrazi said at a United Nations conference on non-proliferation.

Enrichment is a process to concentrate uranium, typically through the use of centrifuges. Enriched uranium can be used as fuel in a nuclear power plant, but if enriched to high levels it can be used as material for an atomic bomb.

The attempt to wring additional incentives from Washington corresponds with a crucial period for the EU-Iran talks. Iranians will vote June 17 in a presidential election. With efforts to master nuclear technology popular among Iranian voters, the EU believes that chances for possible compromise by Teheran are better after the election.

The United States backs the European negotiating effort but has declined to go beyond incentives offered earlier this year. The administration has said it will support Iran's application to join the World Trade Organization and will sell the country spare parts for its aging, US-built commercial airline fleet if Teheran agrees in the EU talks to end its quest for uranium enrichment technology.

The European request for additional incentives sought few specifics and was apparently motivated by a general lack of progress in the talks between Iran and the countries known as the ``EU3'' - Britain, France and Germany.

``Because things aren't going well, they want more out of us,'' the official said. ``They would like to turn this from an EU3 to an EU-US4, but that won't happen. Our approach has not changed.''

A European official visiting Washington last week said the EU3-Iran talks have a ``a 50-50 chance of success,'' but ``we'd enhance these chances if we could add US carrots.''

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