At the foot of the Khyber Pass, a few miles from Pakistan's border with Afghanistan, there is a sign that reads: “Anybody who was ever anybody passed this way.”

Alexander the Great came through here in 326BC, as did Genghis Khan in 1221AD. The British went the other way in 1839 and the CIA funneled arms through here to the Mujahideen in the 1980s.

Today the 30-mile mountain passage is once again at the centre of an historic conflict - this time between Nato and Islamist militants - that will decide the future of this region. In the past few months, militants have started hijacking the convoys that bring in 70 per cent of supplies for Nato and US forces in Afghanistan, and most of the food aid. Fifteen miles away, in Peshawar, they set fire to 260 lorries on two nights this week.

Pakistani authorities shut the pass for a week recently and began providing armed escorts for some of the 200 to 300 lorries that cross the Afghan border every day, but they cannot guard all the convoys, embroiled as they are in their biggest offensive against al-Qaeda and Taleban militants in neighbouring tribal regions. In addition, Pakistan is poised to withdraw its forces from the Afghan border if India responds militarily to last month's Mumbai attack.

The viability of the Khyber Pass dependson the complex network of Pashtun tribes in the surrounding area. “If we're talking about a permanent cure, these escorts won't work,” said Hameedullah Jan Afridi, a federal Minister and leader of one of the main tribes in the Khyber area. “We need to consult the elders and restore the authority of the political administration.”

The pass lies just inside Khyber Agency, one of Pakistan's seven Federally Administered Tribal Areas which have been quasi-autonomous since Pakistan's independence in 1947. The area has traditionally been controlled by the Afridis, a tribe of about 600,000 people.

The Government rewards them for allowing traffic to pass freely by hiring their tribesmen as khasadars, or tribal police. This year, however, the system has been disrupted by disputes between sub-tribes and other groups vying for control of the three main sections of the road - Bara, Landikotal and Jamrud.

The trouble began when Mangal Bagh, a Sepah Afridi who leads a fundamentalist Islamic movement in Bara, sent his men into Landikotal and Jamrud. A former lorry driver, he said he wanted to stop smugglers bringing in liquor and other illegal goods.

Although he denied links to the Taleban and al-Qaeda, he boasted of commanding 120,000 armed men and threatened to take control of all of Khyber. The Government sent paramilitary forces into Khyber in June and pushed him back to Bara. Other tribes appear to have joined forces with local criminal gangs while some believe the Taleban are deliberately targeting Nato supply lines.

Either way, the breakdown in law and order can been measured in the value of goods stolen or destroyed: 36 Nato fuel trucks in March, four US helicopter engines in April, two Humvees and water tank trailers last month, 260 lorries this week.

The World Food Programme, which used to ship 3,000 tonnes of wheat through the Pass daily, has lost $320,000 (£210,000) of food aid in raids in northwestern Pakistan so far this year.“We're looking for alternative routes,” said Wolfgang Herbinger, the WFP head in Pakistan.

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