They were speaking on the eve of a meeting here Wednesday between EU foreign policy chief Javier Solana and Iranian nuclear negotiator Ali Larijani to see if talks are possible between Iran and six world powers which last June offered economic, technical and security benefits if Iran suspended uranium enrichment.

Tehran has defied two Security Council resolutions for it to suspend enrichment, which makes what can be fuel for civilian power reactors or the raw material for nuclear bombs.

The six states -- the five permanent UN Security Council members Britain, China, France, Russia and the United States, plus Germany -- fear Tehran is using what it says is a peaceful effort to generate electrictiy as a cover for the development of nuclear weapons.

"If a solution can be found, it will cost the price of suspension," a European diplomat said.

A second diplomat, who like the first required strict anonymity to discuss confidential issues, said Solana was trying to probe "if real talks can begin."

One idea would be for Iran to declare a moratorium on moving beyond activities it has already started, such as installing and running some 1,300 centrifuge machines as it seeks to upgrade from current research levels of enrichment to industrial production.

The moratorium could open the way for further talks with Solana, with the UN Security Council holding off on further sanctions against the Islamic Republic as long as Iran implements a full suspension of enrichment work.

A Western diplomat said the key was to find a way "for Iran to halt its program in a way that they are not merely stalling for time" in order to move forward again with their nuclear ambitions.

"The key question is whether there is any formulation for suspending enrichment that the Iranians feel they can live with," the diplomat said, expressing doubts that this could happen.

The diplomat said talks with the five permanent Security Council members plus Germany would not in any case start before Iran suspends enrichment.

"Suspension does not mean dismantling what they have built," the diplomat said, adding that it was mainly about stopping the centrifuges from spinning in the refining of the U-235 isotope that makes for enriched uranium as well as keeping the Iranians from learning how to run centrifuges.

Iran says it is merely exercising its right to nuclear energy under the Non-Proliferation Treaty (NPT).

The Security Council has levied low-key measures against Iran, such as banning travel by Iranian nuclear officials, with the option open to impose tougher punishment that could include international economic sanctions.

Diplomats said they doubted whether Iran, despite reported divisions among hardliners and more moderate elements in Tehran, was ready to compromise.

The United States held firm Tuesday to demands that Iran freeze all its uranium enrichment activities.

"There is no change in our policy -- Iran needs to suspend its enrichment-related activities if it wants to enter into negotiations," said Gonzalo Gallegos, a State Department spokesman.

Earlier this month Iran announced that it was on its way to setting up some 3,000 centrifuges at a protected underground site in Natanz. It confirmed plans to eventually have a total of 54,000 centrifuges running there, a level of enrichment that could produce some 20 nuclear bombs a year.

But US officials and non-proliferation experts doubt the Iranians have mastered the difficult technique of actually enriching uranium.

Iran has dampened hopes of a breakthrough in the talks in Ankara by insisting it has no intention of yielding to the West's demands.

"Why are they emphasising that Iran should suspend even for a month?" President Mahmoud Ahmadinejad said in an interview Monday with Iran's Arabic-language television Al-Alam.

Iran faces a new Security Council deadline in one month to suspend enrichment, after which more sanctions could be imposed.

The United States has not ruled out a military attack to bring Iran to heel.

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