President George W Bush has enlisted British special forces in a final attempt to capture Osama Bin Laden before he leaves the White House.

As Mr Bush arrived in Britain today on the final leg of his eight-day farewell tour of Europe, defence and intelligence sources in Washington and London confirmed that a renewed hunt was on for the leader of the September 11 attacks. “If he [Bush] can say he has killed Saddam Hussein and captured Bin Laden, he can claim to have left the world a safer place,” said a US intelligence source.

The Special Boat Service (SBS) and the Special Reconnaissance Regiment have been taking part in the US-led operations to capture Bin Laden in the wild frontier region of northern Pakistan. It is the first time they have operated across the Afghan border on a regular basis.

The hunt was “completely sanctioned” by the Pakistani government, according to a UK special forces source. It involves the use of Predator and Reaper unmanned aerial vehicles fitted with Hellfire missiles that can be used to take out specific terrorist targets.

One US intelligence source compared the “growing number of clandestine reconnaissance missions” inside Pakistan with those conducted in Laos and Cambodia at the height of the Vietnam war.

America rarely acknowledges the use of Predator and Reaper drones, but the most recent known strike was on a suspected al-Qaeda safe house in the Pakistani province of North Waziristan earlier in June. Villagers said the house was empty.

Intelligence on the whereabouts of Bin Laden is sketchy, but some analysts believe he is in the Bajaur tribal zone in northwest Pakistan. He has evaded capture for nearly seven years. “Bush is swinging for the fences in the hope of scoring a home run,” said an intelligence source, using a baseball metaphor.

A Pentagon source said US forces were rolling up al-Qaeda’s network in Pakistan in the hope of pushing Bin Laden towards the Afghan border, where the US military and bombers with guided missiles were lying in wait. “They are prepping for a major battle,” he said.

The main operations in Pakistan are being undertaken by Delta, the US army special operations unit, and the British SBS.

Special forces are being sent to capture or kill al-Qaeda and Taliban fighters based on intelligence provided by the Special Reconnaissance Regiment and its US counterpart, the Security Co-ordination Detachment.

The step-up in military activity has increased tensions between Pakistan and the US. A senior Pakistani government source said President Pervez Musharraf had given tacit support to Predator attacks on al-Qaeda.

Robert Gates, the US defence secretary, said last week that the US would “partner [the Pakistanis] to the extent they want us to” to combat insurgents.

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