It would work strenuously to foment a revolt against the ruling theocracy by Iran’s “hugely dissatisfied” population, a senior official has told The Times.

The United States would not use military force, as in Iraq, but “if Bush is re-elected there will be much more intervention in the internal affairs of Iran”, declared the official, who is determined that there should be no let-up in the Administration’s War on Terror.

To what extent the official, known to be hawkish, was speaking for the White House was unclear, but his remarks are nevertheless likely to cause alarm in Europe. He hinted at a possible military strike against Iran’s nuclear facilities, saying that there was a window of opportunity for destroying Iran’s main nuclear complex at Bushehr next year that would close if Russia delivered crucial fuel rods. To destroy Bushehr after the delivery would cause huge environmental damage. The rods would allow the Iranians to obtain enough plutonium for many dozens of nuclear weapons, he said.

The official also stepped up the pressure on Britain, France and Germany to take a tougher line on Iran, voicing the disdain within the Administration for the Europeans’ attempt to defuse the Iranian nuclear threat through diplomacy. Britain had joined the effort in order to demonstrate its European credentials, he said. France and Germany had teamed up with Britain because they realised that the pair of them could no longer run Europe alone.

Washington believes that the trio has been embarrassed by Iran’s failure to hold good to a deal it struck with the Iranian regime last October. Iran pledged to give UN inspectors the freedom to make snap inspections, and also to suspend uranium enrichment.

Since then, some members of the Administration have begun referring in private to Britain, France and Germany as “the Tehran three”, and to Jack Straw, the Foreign Secretary, as “Jack of Tehran”.

If the Europeans fail to get Iran to back down at a meeting this month, the US wants to close the gap between the rival diplomatic approaches and refer Iran to the United Nations Security Council.

Russia is due to deliver the first shipment of nuclear fuel to Iran early next year for insertion into the reactor at Bushehr before the end of the year.

Despite that, the official believes that “it is not impossible to get Russia to see it our way” and back a UN resolution that would “raise the international saliency” of Iran’s nuclear ambitions. He is convinced that Iran is afraid of a “conveyor belt” that would lead inexorably to sanctions and even military action.

Iran is one of the three members of President Bush’s “axis of evil” and has further angered Washington with its covert interference in Iraq since the end of last year’s war to topple Saddam Hussein.

The official dismissed suggestions that Washington would hesitate to seek regime change in Iran, given the problems it has encountered in Iraq, and Colin Powell, a restraining influence as Secretary of State, will not be serving a second term. It is less clear how the Administration could foment a revolution without uniting Iranians against “the Great Satan”.

The official claimed that more than its dislike of the mullahs, the Iranian population was dissatisfied with an economy that did not have jobs for the young: 60 per cent of the population is under 24.

There is little organised opposition inside the country and financing it directly or through front organisations would probably play into the hands of the mullahs anyway.

At present the US relies on about a dozen Farsi satellite television and radio channels in the San Fernando Valley, California. They beam pirate broadcasts to the estimated seven million Iranians with illegal satellite dishes.

Last year Washington also set up a Persian-language Voice of America programme that is broacast into Iraq. The internet offers another channel for US propaganda, but efforts to impose stiff sanctions or fund anti-Government exile groups have been frustrated by a Republican split over the relative merits of confrontation or engagement.

Despite the US threats one of Iran’s top ruling clerics vowed yesterday that the Islamic republic would continue to pursue its controversial nuclear programme. “We are resolute. It is worth achieving it at any cost,” Ayatollah Ahmad Jannati, head of the Guardians Council, said.

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