The Pakistan sanctuary as well as the 'safe haven' the militants enjoy with the Al-Qaeda in the tribal areas along the troubled Afghanistan-Pakistan border are posing a 'huge challenge' to US and North Atlantic Treaty Organisation (Nato) troops defending the administration of Afghan President Hamid Karzai, the official told reporters on Friday.

'We believe that the Taleban's shura (consultation) council leaders led by Mullah Omar reside in Quetta in Pakistan,' he said, referring to the capital of rugged Baluchistan province bordering Afghanistan.

'They run the shura council, they run the strategic command and control out of the city of Quetta,' said the official, speaking on condition of anonymity.

The Taleban was ousted in a US-led invasion in 2001, after the Sept 11 terror attacks masterminded by Al-Qaeda, whose chief Osama bin Laden and other leaders were given sanctuary by the extremist regime.

More than six years after the ouster, US and Nato-led troops are still waging an uphill battle keeping the Taleban at bay.

Pakistan has repeatedly denied the presence of Osama or Omar in its territory. Washington has placed a multi-million dollar bounty on Omar's head.

The United States had seen clear links between the insurgency in Afghanistan and Pakistan through the Pashtun group, an ethnic minority numbering 39 million along the troubled Pakistan-Afghanistan border, the US official said.

'We also know that there are very clear Pashtun tribal links up through the Federally Administered Tribal Areas, the Fata, especially in north and south Waziristan, where Pashtuns who live in Pakistan are supporting Pashtuns, who are fighting in Afghanistan.

'In some cases, they are the one and same people - they live in Pakistan, they commute to the fight, they fight for a while in Afghanistan and retreat back into safe haven inside Waziristan,' the official said.

He said that the Taleban and Al-Qaeda over the last six months had not only taken up their fight from their 'safe haven' west into Afghanistan but also into the east, into the areas of Pakistan itself.

Underscoring concerns over the militant groups' logistical gains was the December assassination of former premier Benazir Bhutto in Rawalpindi, a city where the army has its headquarters, about seven miles from the capital Islamabad, he said.

CIA Director Michael Hayden said last month that suspected Al-Qaeda militants and allies of Pakistani tribal leader Baitullah Mehsud were behind Ms Bhutto's murder and warned of a 'newly active alliance' between Pakistani and international terrorists against President Pervez Musharraf's administration.

'Now you have a Pashtun-based insurgency that is fighting to regain control of Afghanistan, retaining safe haven, protecting its safe haven in the Fata and in some cases has now declared open hostilities with the Pakistani government as well,' the US official said.

'So, you have got this sort of layering of insurgencies here that really makes this both geographically, politically and militarily a very complex setting,' he said. 'It is a huge challenge.' -- AFP