For the past year, the European Union's so-called "big three" -- Britain, France and Germany -- have been trying to convince Iran to fully answer fears it is seeking to develop nuclear weapons under the guise of an energy programme.

This has met with some tangible results -- Iran has signed an additional protocol to the nuclear Non-Proliferation Treaty (NPT) allowing tougher inspections, and diplomats say the UN nuclear watchdog now has a "better understanding than ever before" of the Islamic republic's activities.

But the Europeans have been pressing for more than just that, and their soft-focus diplomacy is running out of steam as critics accuse the Iranians of playing for time.

In effect, they accept Iran's right to generate atomic energy, but want the country to give up dual-use activities in the nuclear fuel cycle.

The process of mining uranium, converting and then enriching it is perfectly legal under the NPT, the treaty overseen by the International Atomic Energy Agency (IAEA), as long as it is for fuel for reactors.

But once mastered, the fuel cycle can also provide Iran with the "option" of developing a nuclear bomb -- and few diplomats give much credence to assertions from Iranian officials that they have no interest in such an arsenal.

"What we want is for the Iranians to immediately and totally suspend all activities related to enrichment," said a senior Tehran-based diplomat of one of the three European powers.

The Europeans are currently trying to push through an IAEA resolution urging a halt to fuel cycle work in Iran but the clerical regime sees enrichment as a "legitimate right" not to be surrendered.

"We are reaching the moment of truth. If the Iranians are clever, they will keep a low profile until (the next IAEA meeting in) November, especially in view of the upcoming (US) presidential elections," said the diplomat.

"But if they reject such a resolution, it will multiply by four or five the chances of this being referred to the UN Security Council," he said, adding he had the impression that Iranian rhetoric was covering up a desire to negotiate.

The United States may want to see Iran hauled before the Security Council for possible sanctions, but the Europeans detect risks.

"Sanctions have a poor reputation after Iraq. The whole issue of pre-emption is also tough to swallow for the Europeans (and) there are fears that pushing Iran too far without going through the diplomatic motions would be counterproductive," said another European diplomat.

"There is also the feeling that the region is, frankly, in such a mess already. There are worries that Iran could make things worse in Iraq, Afghanistan, Lebanon, etc. We just don't need that at the moment."

The source also pointed out that "there is no guarantee of consensus at the Security Council", given that there is "no smoking gun -- only a broader trend" that creates supsicions of a nuclear weapons drive by Iran.

"There is a sense that we are heading in the direction of the UN Security Council. But going to the UN is quite a drastic step and is not a move that can be made overnight. Don't forget that Iraq took years and several smoking guns, and there was still very little consensus."

Added another diplomat: "The question is what we do when we get to the Security Council."

Diplomats have spoken of a resolution "forbidding Iran to work on the fuel cycle due to a threat to international security", but have pointed out that "that needs to be backed up by credible sanctions if Iran does not comply".

"Economic sanctions are out. Military action is almost unthinkable. Political sanctions are possible. But we're not there yet."

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