Thousands of Pakistani troops were massing for an assault on Taleban positions 65 miles from the country’s capital last night after giving the insurgents 24 hours to withdraw from their advanced positions or face attack.

The threat of force follows a stern warning from American policymakers that Islamabad was doing too little to stem a growing militant insurgency.

Richard Holbrooke, the special US envoy for the region, called Pakistan’s President Zardari on Thursday to convey Washington’s concern. Hillary Clinton, the US Secretary of State, accused Pakistan this week of “abdicating to the Taleban”, which “poses a mortal threat to the security and safety of our country and the world”.

The US considers rooting out militant sanctuaries in Pakistan critical to success in the Afghan war. Washington is also worried about the security of Pakistan’s nuclear weapons

Mrs Clinton’s remarks followed a recent deal between Mr Zardari and the Taleban in the Swat Valley, allowing them to establish a fundamentalist enclave in the former tourist area in exchange for laying down their arms.

The Taleban have not disarmed, and this week its fighters poured out of Swat into the neighbouring district of Buner, taking control of government buildings and digging in at strategic positions around the major towns.

The threat from the army has so far been enough to encourage some insurgents to start pulling out of Buner, but other fighters were holding positions in the hills.

Local government officials said that militants were seen leaving a high-walled villa that served as their headquarters in Buner, in the foothill of the Karakoram mountains. The black-turbaned fighters carrying automatic weapons and rocket-propelled grenades clambered into several trucks and minibuses before driving away.

Taleban commanders insisted that their fighters had been preaching peacefully for Islamic law. Muslim Khan, a spokesman for the Taleban, said the fighters were leaving “of their own accord, not under any pressure”.

There was no indication that the insurgents were willing to give up control of the mosques and seminaries that they have been using to recruit local youths. A senior officer said that troops had been ordered to eliminate insurgents who refused to surrender.

In an unusually tough statement General Ashfaq Kayani, the head of the army, declared that the military was determined to root out the menace of terrorism and would not allow the militants to dictate terms to the Government or impose their way of life on the civil society of Pakistan.

“The army will fight to eliminate the militants who endanger the security of the country,” he said, addressing senior commanders in Rawalpindi.

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