"There will be a further discussion within the next weeks," Iranian negotiator Sirus Nasseri told reporters.

Iran had threatened to break off the talks that had begun in December if Wednesday's meeting in Paris failed to make progress, a reference to European promises of trade, technology and security rewards if Iran would give up on uranium enrichment.

Enriched uranium can be used as fuel for civilian nuclear reactors but can also be the explosive core of atomb bombs.

Nasseri said the talks had ended without reaching a final accord. "Each side still has its own views."

But one European diplomat told AFP that the atmosphere at the meeting was "positive and constructive", and another said a main goal Wednesday was just to keep the process going.

"The longer the talks last, the better it is," the second diplomat said.

Nasseri said however that Iran felt that "time is of the essence and we need to see progress."

European diplomats said they had expected Wednesday's talks, a review of progress after three months of negotiations, to be inconclusive but not to scuttle the process, especially with the Iranians unable to take firm positions ahead of presidential elections in their country in June and with what is likely to be a long negotiating process still in its early stages.

The United States, which wants to haul Iran before the UN Security Council for what it says is a covert nuclear weapons program, has softened its stance and agreed to support European countries in offering the Islamic Republic incentives if it gives up enrichment.

Washington has said Europe will now support it in bringing Tehran to the Security Council if the talks fail.

Iran suspended enrichment in November as a confidence-building measure to get the talks going but refuses to permanently abandon the process, saying it has a right to make nuclear fuel under the provisions of the nuclear Non-Proliferation Treaty.

Nasseri has previously said that the Europeans were not pressing Iran on this issue but he said Wednesday "as you know the Europeans have a view on that (enrichment)."

He said the purpose of the talks was "to have a mutually acceptable agreement on firm and objective guarantees and this would be the focus of discussion for the weeks ahead of us."

EU negotiators Britain, France and Germany said in a joint statement released after the meeting that Iran had "presented certain ideas on objective guarantees that Iran's nuclear program is exclusively for peaceful purposes."

It said that so far the three months of talks "contribute to an enhanced relationship between the E3/EU and Iran and set the stage for further progress in our negotiations."

"We have had quite a bit to do because we have needed to have an assessment of the work that has been done during the last three months but more so we have had to focus on what lies ahead," Nasseri said.

"Essentially what I can say is that our nuclear fuel production program, the pace, content and context could be discussed in a manner that perhaps could provide a better possibility for confidence and assurance," Nasseri said.

He did not give details.

European diplomats have said ideas being floated by Iran include letting it enrich uranium only to a low grade -- not to weapons level -- and allowing extensive inspections of its facilities by the International Atomic Energy Agency.

Tehran also might propose giving the United States a half share in any enrichment facility, the diplomats said.

A third option might be an Iranian offer to build a pilot uranium enrichment plant with only 2,000 centrifuges instead of the 54,000 that Iran had proposed for an industrial-level facility.

But the diplomats said that neither the United States nor Europe would accept Iran keeping an enrichment capability, as this would leave it with the capacity to "break out" and make nuclear weapons.