WE HAVE been here before. But today there may finally be a dramatic step forward in the three-year battle to prise Iran away from its nuclear ambitions.

The board of the International Atomic Energy Agency (IAEA) meets today in Vienna to decide whether Iran should be hauled before the United Nations Security Council for refusing to abandon its nuclear programme. After all the “last chances” which the IAEA has given Iran, this one looks most worthy of the term.

Iran may finally have reached the end of the road after talks on Friday — called at Iran’s request — failed to make a breakthrough.

The so-called EU3 — Britain, France and Germany — rejected the “compromise” Tehran offered, although it signalled that it would use the weekend to explore with Russia whether any deal might still be done.

But that looked unlikely to yield anything acceptable to the US and Europe. For months, Russia had seemed to offer Iran the only way out of referral to New York.

It proposed doing the most controversial nuclear work on its territory, allowing Iran to run nuclear power stations but not to master the technology which could also give it weapons. But Iran insisted on holding on to “experimental” work — a condition unacceptable to the EU3.

The IAEA voted, at an emergency meeting in February, to press ahead with the referral to the Security Council, allowing a month’s delay to see how Iran would respond. “Not well enough”, appears to be the result of that experiment.

Gary Samore, a specialist on nuclear proliferation at the MacArthur Foundation in Chicago, said: “At this point it looks like Iran’s efforts to split the P5 [Britain, France, Germany, the US and Russia] have failed. So the board should be able to confirm the February IAEA resolution to toss the issue to New York.”

On Saturday, in Pakistan, President Bush said that he would no longer oppose a gas pipeline which Iran wants to build to India through Pakistan. It would give India gas and Pakistan transit fees.

He said that he wanted to make clear that the US’s dispute with Iran was over its 20-year covert nuclear programme, not its wider commercial activities.

Bush’s offer, very different from his unequivocally hostile attitude three years before, is a clever move.

It marks an attempt to explore whether Iran would be open to a deal — but also to court support from other countries if it is not.

If Iran were referred to the Security Council, what would happen next? European governments and the US have spent a lot of effort on this in the past month. The first step would be to press the Council for a resolution ordering Iran to stop uranium enrichment, the most controversial aspect of the work. It would also order Iran to comply with the IAEA’s “additional protocol” — allowing the agency’s inspectors to make short-notice visits to sites of their choosing.

In Samore’s view, if the Council did this, “presumably, Iran would reject the Security Council’s request. The Council would then need to consider how to enforce its authority, including political and economic sanctions. This would be a critical test of the Council’s ability to achieve non-proliferation objectives.”

Many have been sceptical of the Council’s ability to do that. But diplomats have drawn up a long list of options, beginning with “cultural” sanctions, such as stopping football-mad Iran competing in the World Cup or stopping its ambassadors from travelling. A ban on the sale of equipment for its oil industry would also be high on the list. Western diplomats have emphasised that the UN would never target ordinary Iranians through food or medicine sanctions.

Before the Iraq war the US moved briskly and impatiently through the process of getting UN approval — and failed. With Iran, it and Europe are moving extremely slowly, needing to build up support.

Today will show whether, after three years, they have got one stage further.

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