"Despite all our efforts we were not able to reach a conclusion, ambiguities still exist in some of the main issues," said the head of the Iranian negotiating team, Sirus Nasseri.

"On the nuclear issue, which is the main issue, the topic of objective guarantees is not clear," he told state television.

"We have said that we will continue to produce our fuel, it is our right according to international regulations... the only thing we can offer them is assurances that our activity is not going to be of military use," Nasseri said.

Nuclear talks between Iran and the EU ended Friday in Geneva apparently still deadlocked over Europe's demand that Tehran give up uranium enrichment, a fuel process which can also make atomic bombs, diplomats said.

The EU said the talks had made slower progress than expected and warned Tehran of the risk of being referred to the United Nations if they failed.

However, in a new turn of events, the United States said Friday it would drop objections to Iran joining the World Trade Organization even as President George W. Bush warned Tehran it must abandon any quest for nuclear weapons.

US Vice President Dick Cheney meanwhile said Iran must end any nuclear weapon ambitions or run the risk of "stronger" US action.

Iran and the so-called EU-3 of Britain, France and Germany have held four rounds of negotiations since December, a month after Iran agreed to a temporary suspension of uranium enrichment to back up its claim that its atomic program is strictly peaceful.

The Europeans are seeking to persuade the Islamic republic to end its uranium enrichment drive in return for economic, technological and political incentives.

Nasseri said experts from both sides would probably meet next week ahead of a new round of talks to be held later this month.

"While progress is not as fast as we would wish, we believe we are moving in the right direction ... and that we should have at least preliminary results to show from the negotiations in the period ahead," the EU-3 said in a report.

The report said that if Iran continues to suspend enrichment activities and that is verified by the UN's nuclear watchdog the International Atomic Energy Agency, the issue could be resolved by IAEA governors.

"If on the other hand, despite our efforts Iran does not do so, then as has been implicit in the agreements reached with Iran and well understood by all concerned, we shall have no choice but to support referring Iran's nuclear programme to the UN Security Council," they said.

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