Iran made the written proposal to be allowed to run a pilot centrifuge project for uranium enrichment at a meeting in Paris on Wednesday with EU negotiators Britain, France and Germany, according to a European official who asked not to be named.

The European trio 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."

But neither they nor Iran provided details.

Iran's foreign ministry spokesman Hamid Reza Asefi said Thursday that the proposal it has made to the European Union on easing international concerns over its nuclear programme demonstrated the Islamic republic's "seriousness" in resolving the issue.

Iran suspended uranium enrichment in November as a confidence-building measure to get EU-Iran talks going.

But it refuses to permanently abandon enrichment, saying its nuclear program is peaceful and pointing out that it has a right to make nuclear fuel under the provisions of the nuclear Non-Proliferation Treaty, regardless of US charges that Tehran is secretly developing atomic weapons.

The pilot plant would have a relatively small number of centrifuges, the officials said.

Centrifuges, placed in sequence, refine increasingly enriched uranium with each cycle.

In highly refined form, the substance can be used in the explosive core of nuclear weapons, but less refined forms of enriched uranium can be fuel for civilian nuclear reactors.

Experts have told AFP the pilot plant would have 500 to 2,000 centrifuges instead of the 54,000-centrifuge cascade Iran has said it wants to build.

The Iranians said they would allow close monitoring of a pilot facility by the Vienna-based International Atomic Energy Agency (IAEA), the official said, adding that the European trio would "look at this (proposal) with experts."

"If the experts find a way to monitor this in an effective way, then why not?" the official said.

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

US officials however say that if Iran is allowed to keep any sort of enrichment capability, it would gain the capacity to make nuclear weapons.

The Europeans told the Iranians on Wednesday that "for us it is clear Iran should not be doing enrichment," the European official said.

The European trio made it clear that Tehran must give "objective guarantees that (the Iranians) take away from their nuclear program everything that can be dangerous" in terms of nuclear weapons proliferation, the official said.

The official noted that this referred not only to uranium enrichment but also to reprocessing spent fuel, a process that can extract plutonium, which also can be used to make nuclear weapons.

But a senior European diplomat told AFP: "If you want to have an agreement, both sides will have to compromise."

The diplomat insisted that "the sheer fact that this (the Iranian proposal) is being studied does not mean it is accepted."

"The only meaning of what is happening is that the negotiating process is alive and kicking. There is something to be discussed," the diplomat said.

Iran and the European trio agreed Wednesday to continue their nuclear talks despite having failed to secure an agreement on uranium enrichment.

Tehran had previously threatened to break off the talks that had begun in December if Wednesday's meeting in Paris failed to make progress, but both sides praised the encounter as constructive.

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