Mounting fears that the United States will do nothing to prevent Iran becoming a nuclear power will be outlined by Ehud Olmert, Israel’s prime minister, when he meets President George W Bush in Washington tomorrow.

Israel is concerned that Bush will pass the Iranian hot potato to Barack Obama, the president-elect, while the last chance of destroying Tehran’s nuclear bomb-making programme may be passing.

A Pentagon source told The Sunday Times earlier this year that Bush had given Israel an “amber light” to carry on with military preparations to attack Iranian nuclear sites.

According to Israeli intelligence sources, Iran has sufficient nuclear material to make an atomic bomb. “They are working on three programmes at once,” said the sources. “They are speeding up their centrifuges to enrich uranium, calibrating a warhead to fit their ballistic missiles and improving the range and accuracy of their ballistic missiles.”

The International Atomic Energy Agency, which has been inspecting Iran’s main nuclear facility at Natanz, published a report last week which concluded that Iran is rapidly increasing stockpiles of enriched uranium and may be on course to build a nuclear weapon by next year.

In the baking heat of the Negev desert, the Israeli air force’s top guns are training for a secret mission. No one here knows if, or when, a raid will get the political go-ahead but the pilots say it could be their third attack in three decades on a nuclear plant and easily the most dangerous.

On the runway an F-16 fighter jet was preparing to take off. In the cockpit was a 25-year-old pilot whom we have agreed to call Captain M.

“I knew I was flying the special one,” said M, referring to the nuclear symbol painted on the fuselage to mark a “kill” 27 years ago when two bombs were dropped, each weighing a ton, on Saddam Hussein’s Tammuz nuclear reactor near Baghdad, destroying it completely.

In a further indication that this squadron is preparing for conflict, 80 US technicians based at the nearby Nevatim air base in the Negev have installed the world’s most advanced X-band radar system, with a range of 1,250 miles, that will hugely enhance Israel’s tactical capacity in the air.

There is a grave mood among the pilots, who know they may soon be sent to defend their country. “We feel the future of Israel isn’t safe and we want to do what we can to defend it,” said one.

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