It is seven o’clock in the morning eastern standard time when the news comes through to Americans at their breakfast tables. President George W Bush will shortly be addressing the nation live from the Oval Office. Moments later he is on air, announcing in a sombre drawl that Iran’s nuclear sites have been struck during the night by American bombers.

“You can see the shape of the speech the president will give,” said Richard Perle, a leading American neo-conservative. “He will cite the Iranians’ past pattern of deception, their support for terrorism and the unacceptable menace the nation would present if it had nuclear weapons.

“The attack would be over before anybody knew what had happened. The only question would be what the Iranians might do in retaliation.”

Sounds far-fetched? Think again. The unthinkable, or what Jack Straw, the foreign secretary, described only a few weeks ago as “inconceivable”, is now being actively planned in the Pentagon.

White House insiders say that Bush and Dick Cheney, his hawkish vice-president, have made up their minds to resolve the Iranian crisis before they leave office in three years’ time.

They say that military intervention — in the form of a massive strike against Iran’s nuclear facilities — is being planned and that Bush is prepared to order the raid unless Iran scraps its nuclear programme.

“This White House believes that the only way to solve the problem is to change the power structure in Iran, and that means war,” a senior unnamed Pentagon adviser is quoted as saying in an article by Seymour Hersh, the respected American investigative journalist, in tomorrow’s New Yorker magazine.

The Sunday Times was last week given the same message. A senior White House source said Bush and Cheney were determined not to bequeath the problem of a nuclear Iran to their successors. “It’s not in their nature,” he said.

White House insiders scoff that Bill Clinton left Al-Qaeda unchecked. A nuclear-armed Iran, they believe, is too dangerous to be left to a potential Democrat president.

One date is said to be etched in the minds of military planners: 2008. Word has gone out that the Iranian nuclear crisis must be resolved by then or the regime of President Mahmoud Ahmadinejad, with its Israel-baiting rhetoric, will face military consequences.

Hersh reports that one option involves the use of a bunker-buster tactical nuclear weapon, such as the B61-11, to ensure the destruction of Iran’s main centrifuge plant at Natanz.

The Sunday Times understands that a strike with a conventional weapon is much more likely. By 2008 a new bunker-busting missile called the Big Blu should be available to the US air force. The 30,000lb behemoth is being designed for dispatch by the B-series stealth bombers and can penetrate 100ft under the ground before exploding.

Trident ballistic missiles, newly converted to carry conventional warheads, may also be on hand by 2008, providing Bush with further options.

What is going on at the White House? Is Bush really contemplating a strike against Iran or might his officials simply be talking up the possibility to strengthen their negotiating hand with Iran? If military action were to be launched, what would be the consequences for America, the Middle East and Britain?

UNTIL Ahmadinejad won the Iranian presidency on a tide of popular support that caught the West by surprise last June, Iran had been seen by many commentators as being on the mend.

American neo-cons had hoped the invasion of Iraq would set in train a domino effect across the region, with the people of Iran and other oil-rich states rising up to demand western-style freedoms and democracy.

Unfortunately the reverse has been true, in Iran at least. Since taking power, Ahmadinejad has openly embraced a tide of nationalism and anti-Israeli and American sentiment.

The rhetoric has been matched with action. He has restarted Iran’s nuclear enrichment programme, placing the country in breach of its international obligations and on a collision course with the West.

Seemingly emboldened by America’s problems in Iraq, last week Ahmadinejad continued his baiting of the West by staging ostentatious war games in the Gulf.

The hardware on display — flashy missiles, torpedoes and rockets — may be no match for US weaponry, but it served as a warning of the disruption that the regime could cause to the global economy by blocking the Straits of Hormuz, the corridor through which much of the Middle East’s oil flows.

“The importance of the ‘Great Prophet’ manoeuvre lies in the time and geographical place as well as the arms used,” General Yahya Rahim Safavi, head of Iran’s elite Revolutionary Guards, said pointedly.

Revelling in the international spotlight and apparently oblivious to his growing pariah status, Ahmadinejad will this week up the anti by hosting an international conference focused on Palestine and “the Holocaust myth”.

IT IS against this backdrop and in the context of the race to find a diplomatic solution at the United Nations that the White House is briefing on military action against Iran.

Some observers will interpret it as more posturing than reality.

Nevertheless, the US administration is nothing if not tenacious and there was a growing feeling in Washington last week that Bush really has put a military option on the table. While the British and Europeans are still placing faith in diplomacy, the Americans are actively preparing for the worst case scenario, it is said.

Furthermore, while it is true that setbacks in Iraq have diminished American enthusiasm for military intervention, it would be a mistake to conclude that the American public, with its horror of the ayatollahs and memory of the 1979 embassy siege in Tehran, would not stomach a strike, Bush officials believe.

“The American people are not looking for new fights but they understand the nature of the Iranian threat very clearly,” said a senior American defence official. “I don’t see anyone out there saying, ‘Oh, we have to be nice to Iran’.”

Senior military planners at the Pentagon met recently to assess such an attack’s chances of success. They told the White House that they had yet to map all of Iran’s nuclear enrichment sites and that several were buried under deep granite mountains. A strike now could set the mullahs’ programme back only a couple of years at most.

Fast-forward to 2008 and the picture changes. By then more intelligence will have been gathered on the location of sites. And, crucially, Big Blu should be ready.

The damage, if not total, say experts, would be considerable. “The Iranians need 100% of their programme to build nuclear bombs,” the American defence analyst John Pike, of globalsecurity.org, pointed out. “We don’t have to destroy 100% of their facilities to deny the ayatollahs a nuclear capability.”

Edward Luttwak, a Pentagon adviser and expert on military strategy at the Center for Strategic and International Studies in Washington, is a leading advocate of the theory that Iran’s nuclear installations could be bombed “in a single night”.

Inside the Pentagon, top officials have been citing Luttwak’s views. Air strikes by a handful of B2 bombers, flying out of the British dependency of Diego Garcia in the Indian Ocean, would be enough to demolish the most critical Iranian nuclear sites such as Natanz, Arak and Isfahan.

“You don’t need to solve the problem of Iran, you just need to delay the mullahs for a few years, expose their vainglory and hope that the Iranians, most of whom hate this regime, will get rid of them,” Luttwak said.

It is a tempting prospect for Bush, who is determined to leave his mark on history as a “consequential president”, as Karl Rove, his adviser and guru, once put it. However, there is considerable nervousness among administration officials about the Iranians’ potential reaction.

“We’re in a state of flux about military action,” said a White House insider. “We can bomb the sites, but what then?” Will America hold its nerve if events take a sharp turn for the worse?

IF attacked, there is no doubt that Iran could unleash a wave of terrorism in the West and Israel and destabilise its all-too-fragile Iraqi neighbour. An attack would almost certainly also encourage Iranians to rally behind Ahmadinejad.

Luttwak admits that it would be disastrous if military action were to alienate pro-western Iranians, whom he regards as America’s “once and future allies” in the Middle East.

It is a view shared by many neo-conservatives, including Perle, who would prefer to see internal regime change in Iran rather than bombs raining down.

To this end the State Department has been awarded $75m to promote democracy in Iran. “It’s a safe bet the CIA has been given a budget 10 times that size,” observed Pike.

Last week there were reports that British ministers were to hold secret talks with defence chiefs to consider the consequences of a possible American-led attack on Iran.

The report was denied by Downing Street but there can be little doubt that the apparent change in American thinking must now be occupying minds throughout Whitehall.

Until recently it was assumed that any strike on Iran’s nuclear facilities would be left to the Israelis, who are the most interested party. That, say American defence sources, has changed on the grounds that only the US has the weaponry to perform the job in one night — presenting the world with a fait accompli.

More worrying for Labour perhaps is that under the American plans Britain would be expected to play a supporting role, perhaps by sending surveillance aircraft or ships and submarines to the Gulf or by allowing the Americans to fly from Diego Garcia.

Will Tony Blair still be in Downing Street by 2008 and, if not, would Gordon Brown as prime minister be willing to play ball on yet another military adventure in the Middle East? As public opinion stands, such a move could spell political suicide.

Larry Wilkerson, Colin Powell’s former chief of staff, believes Bush is compounding the mistakes he made in the run-up to the war in Iraq. “If you get to the point where you have to use your military, you’ll want everybody on board with you and we haven’t even tried,” he said.

Such considerations have failed to sway Bush and Cheney before. If their approval ratings remain in the doldrums, there may be an upside to a strike on Iran. “Regardless of how bad Bush’s poll numbers are, Americans love a display of firepower,” said Pike.