If President Bush was able, over dinner last night, to persuade the feuding leaders of Pakistan and Afghanistan to patch up their quarrel and focus on defeating the Taleban, he will have significantly bolstered security in that turbulent region. The public recriminations between President Musharraf and President Karzai are hampering all efforts to counter the resurgent Taleban, seal the border and halt the flow of weapons that is taking a rising toll of allied forces in Afghanistan. Without close co-operation between two leaders who both have Washington’s strong backing, Western attempts to bring peace to the region will come to little.

The quarrel began with President Karzai’s accusations that Pakistan was making little effort to control the long, porous border, allowing Taleban fighters to use Pakistan as a haven and a supply source. President Musharraf was also angered by accusations that Osama bin Laden and other al-Qaeda militants were hiding in the mountainous and semi-autonomous tribal lands of Waziristan and that Pakistan’s Army had failed to find them. The issue is acutely sensitive in Islamabad: despite his volte-face after 9/11 — which President Musharraf claims in his book was the result of US threats to “bomb Pakistan into the Stone Age” — there is lingering support for the Taleban. Within the ISI intelligence service, which helped to create and arm them, there are still Taleban sympathisers. And in the tribal area, there are strong tribal links with Afghan Pashtuns across the border.

The Pakistan Army’s attempt, therefore, to police the border has run into serious opposition. Since 2004 it has had about 30,000 troops in north and south Waziristan and has lost 375 soldiers and militiamen. Under pressure to withdraw, the Government signed a truce with tribal elders recently, under which it will stop attacks on tribesmen in return for their curbing the Taleban and attacks across the Afghan border.

The deal, however, has only exacerbated mistrust of Pakistan’s intentions. Critics in Kabul and Washington say it risks creating safe havens for the Taleban and al-Qaeda. Pakistan has had to deny claims that the deal was approved personally by Mullah Omar, the fugitive Taleban leader; but three Pakistani tribesmen suspected of attacking a US base in east Afghanistan have been released by Pakistani paramilitary troops.

This is the wrong time to cede control of the border. The number of suicide bombings, attacks on government installations and firefights with coalition forces in Afghanistan has risen sharply. There is a clear danger that the Taleban, able to show a freedom of manoeuvre, will win civilian support, through intimidation and a sense of inevitability, for an anti-foreigner jihad and make the south ungovernable. President Karzai gave a clear warning, months ago, of the cost of allied failure to reinforce their missions. Pakistan must seal off the tribal areas urgently so that weapons cannot get through. The war across the border threatens not only Kabul; it also threatens the stability of the entire region.