US prepares military blitz against Iran's nuclear sites

Strategists at the Pentagon are drawing up plans for devastating bombing raids backed by submarine-launched ballistic missile attacks against Iran's nuclear sites as a "last resort" to block Teheran's efforts to develop an atomic bomb.

Central Command and Strategic Command planners are identifying targets, assessing weapon-loads and working on logistics for an operation, the Sunday Telegraph has learnt.

They are reporting to the office of Donald Rumsfeld, the defence secretary, as America updates plans for action if the diplomatic offensive fails to thwart the Islamic republic's nuclear bomb ambitions. Teheran claims that it is developing only a civilian energy programme.

"This is more than just the standard military contingency assessment," said a senior Pentagon adviser. "This has taken on much greater urgency in recent months."

The prospect of military action could put Washington at odds with Britain which fears that an attack would spark violence across the Middle East, reprisals in the West and may not cripple Teheran's nuclear programme. But the steady flow of disclosures about Iran's secret nuclear operations and the virulent anti-Israeli threats of President Mahmoud Ahmadinejad has prompted the fresh assessment of military options by Washington. The most likely strategy would involve aerial bombardment by long-distance B2 bombers, each armed with up to 40,000lb of precision weapons, including the latest bunker-busting devices. They would fly from bases in Missouri with mid-air refuelling.

The Bush administration has recently announced plans to add conventional ballistic missiles to the armoury of its nuclear Trident submarines within the next two years. If ready in time, they would also form part of the plan of attack.

Sen John McCain, the Republican front-runner to succeed Mr Bush in 2008, has advocated military strikes as a last resort. He said recently: "There is only only one thing worse than the United States exercising a military option and that is a nuclear-armed Iran."

Senator Joe Lieberman, a Democrat, has made the same case and Mr Bush is expected to be faced by the decision within two years.

By then, Iran will be close to acquiring the knowledge to make an atomic bomb, although the construction will take longer. The President will not want to be seen as leaving the White House having allowed Iran's ayatollahs to go atomic.