The best part of the resolution against Iran now taking shape is that all the members of the United Nations Security Council will put their names to it. The worst is that the measures to punish Iran's unchecked nuclear ambitions represent only a tiny extra sting that it could shrug off if it chose.

Tehran may not be that insouciant about the censure, however. The gamble behind the resolution — put together by Britain, France and Germany — is that Iran will be alarmed by the unanimity of the council. They hope that even if Iran dismisses the package as only a whisker beyond the purely symbolic (and that judgment would be right), it will fear that worse could follow.

Above all, the tactics rest on the hope that President Ahmadinejad is in such trouble at home over the stuttering economy that Iranians themselves will bring about regime change. It is not a foolish dream but it is one that the West has had about Iran for decades now, to no great end.

Yesterday Ahmadinejad did indeed declare that Iran would ignore the council and press ahead with the contested work regardless of any sanctions. “The Iranian nation has chosen its path and will continue with it,” he said. “Such illegal behaviour [by Western powers] will not divert the Iranian nation from its path.”

The strongest part of the draft resolution is a proposal for mandatory travel restrictions on named Iranians. In the council's earlier sanctions against Iran, these were simply an “exhortation”.

There is also a new clause urging countries “to exercise vigour and restraint” in granting more export credit guarantees to Iran. It means, of course, that it wants them not to grant the guarantees, although there was not enough support for an obligatory clause. The text is aimed at China, which rushed to pick up business when Germany stopped issuing guarantees.

There is a still-unresolved wrangle to prohibit dealing with the Melli and Saderat banks, as well as Sepah bank, already the subject of sanctions. In the past year, financial curbs have proved the most effective tool in alarming Iranians about the consequences of refusing to climb down on their nuclear programme.

Libya's presidency of the Security Council ends this month; the plan of Britain, France and Germany is to push through the resolution under the more amenable Panamanians in February. The US, which has always favoured a more aggressive line than the European three, is firmly behind the plan but is not one of the formal sponsors. It has found it useful, in the five years of bad-tempered diplomacy since Iran's covert nuclear programme came to light, to keep its distance from the European position, if only to keep uncertainty alive in Tehran about whether it might be prepared to take military action.

You would never guess it from Ahmadinejad's public declarations, but others in Tehran are worried about the consequences of his intransigence, as well as his economic mismanagement. On Monday Ayatollah Ali Khamenei, Iran's Supreme Leader, overruled Ahmadinejad in favour of parliament in a dispute about gas supplies to villages. The President's conservative supporters could face tough opposition in parliamentary polls in March, all the more if leading conservatives, and Khamenei, cool in their support.

Additional reporting by James Bone

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