For five years the West has used every diplomatic device at its disposal to entice Iran into complying with strict conditions that would prevent its nuclear programme being diverted to produce an atomic bomb.

Those efforts, however, are now faltering. US leaders are openly discussing the looming conflict. A recent poll showed that 57 per cent of Americans favoured military intervention to stop Iran building a bomb.

Tehran scoffs at threats by the West, has pledged to press on with its nuclear progamme and defend itself if attacked.

The military option may be the only means of halting a regime that has threatened to annihilate Israel from developing a bomb and triggering a regional nuclear arms race.

Experts agree that America has the military capability to destroy Iran’s dozen known atomic sites. US forces virtually surround Iran with military air bases to the west in Afghanistan, to the east in Iraq, Turkey and Qatar and the south in Oman and Diego Garcia. The US Navy also has a carrier group in the Gulf, armed with attack aircraft and Tomahawk cruise missiles. B2 stealth bombers flying from mainland America could also be used.

The air campaign would not be easy. The Iranians have been preparing for an attack. Key sites are ringed with air defences and buried underground. Sensitive parts of the Natanz facility are concealed 18 metres (60ft) underground and protected by reinforced concrete two meters thick. Similar protection has been built around the uranium conversion site at Esfahan.

“American air strikes on Iran would vastly exceed the scope of the 1981 Israeli attack on the Osiraq centre in Iraq, and would more resemble the opening days of the 2003 air campaign against Iraq,” said the Global Security consultantcy.

Lieutenant-Colonel Sam Gardiner, a former US Air Force officer, predicted that knocking out nuclear sites could be over in less than a week. But he gave warning that would only be the beginning.

Iran has threatened to defend itself if attacked. It could use medium-range missiles to hit Israel or US military targets in Iraq and the region. It could also use its missiles and submarines to attack shipping in the Gulf, the main export route for much of the world’s energy needs. “Once you have dealt with the nuclear sites you would have to expand the targets,” said Lieutenant-Colonel Gardiner. “There are another 125 to deal with including chemical plants, missile launchers, airfields and submarines.”

While this huge US offensive is underway Iran would almost certainly deploy its most powerful weapon. It would unleash a counter-attack through proxies in the region. Hezbollah, the Lebanese Shia militia, would attack Israel. Moqtadr al-Sadr, the militant Iraqi Shia religious leader, could order his Mahdi Army to rise up against American and British forces in Iraq. Iranian-backed groups could wreak havoc against Western targets across the world.

What began as a military operation to maintain a balance of power in the Middle East, could instead plunge the region into another conflict.

“It will have to be diplomats, not F15s that stop the mullahs,” said Joseph Cirincione, an expert on non-proliferation at the Carnegie Endowment for International Peace. “An air strike against the uranium conversion facility at Esfahan would inflame Muslim anger, rally the Iranian public around an otherwise unpopular government. Finally, the strike would not, as it often said, delay the Iranian programme. It would almost certainly speed it up,” he wrote in an article.

PUBLIC OPTIONS

‘All options — including the military one — are on the table’

Donald Rumsfeld, US Defence Secretary

‘There is only one thing worse than military action, that is a nuclear armed Iran’

John McCain, Republican senator for Arizona and US presidential hopeful

‘We are not seeking a military confrontation, but if that happens we will give the enemy a lesson that will be remembered throughout history’

Abdolrahim Moussavi, head of Iran’s joint chiefs of staff

‘Give another year to make HEU (highly-enriched uranium) for a nuclear weapon and a few more months to convert the uranium into weapon components, Iran could have its first nuclear weapon in 2009’

David Albright and Corey Hinderstein, Institute for Science and International Security

‘There isn’t a military option. There certainly isn’t one on the table, let’s be clear about that.’

Jack Straw, Foreign Secretary

‘Obviously we don’t rule out any measures at all’

Tony Blair

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