Yesterday a Pakistani security official said that if India now put more forces on to the disputed Kashmir border, the Pakistani Army would do likewise. By the way, that would mean that Pakistan put less effort into fighting the Taleban on its western border, he added, in an unsubtle warning to the US and Britain. Pakistan understands only too well that for the West its border with Afghanistan represents the frontline in the war on terror.

On the Pakistani side priorities are different. As the calls go up for a clampdown on terrorists, Islamabad's most urgent desire is not for a Nato-defined victory, but for a peaceful life on its Afghan border. It is not going to support conflict there at the cost of its own stability. That is a forceful factor in the new US calculations about whether to deal with the Taleban.

Six days after the Mumbai attacks Pakistan finds itself in a difficult position. India's discovery (so it says) of clear links to Pakistani organisations among the terrorists supports the instinctive belief of many Indians that their neighbour is somehow to blame. Other countries must tell Pakistan that tolerance for terrorism is unacceptable, Indian government officials have said. If only it were that simple: a neat story of known agents with clear motives.

That it is murkier, on the Pakistani side, barely needs saying. But it would be folly, on all sides, if the Mumbai attacks were allowed to inflame the old dispute over the Kashmir border. If India and Pakistan now ramp up hostilities, it will be an act of self-indulgence, on each side, that distracts them from fighting terrorism. India's assertion that “external elements” were to blame may well be upheld by evidence, but also distracts attention from the rise of radical religious groups within its own borders.

If it also refuses all international interest in getting the Kashmir dispute resolved - its traditional position - it will be refusing to acknowledge how serious the implications could be, not just for the region but for Britain and other countries that are the targets of terrorism.

Since Wednesday, Pakistan officials have rushed to point out that there is a lot of terrorism in their country and the Government had plenty of reason already to try to defeat it. They point, without need of elaboration, to the Marriott hotel bomb, and to the assassination of Benazir Bhutto (which propelled her widower Asif Zardari on to his current precarious perch as President). Pakistan can also claim, with justice, to have put a lot of effort - and approaching 1,000 military lives - into trying to seal the western border to terrorists.

Then it gets more complicated. We should take with a pinch of salt the frequent public protests by Pakistan officials at US bombing across the Afghan border. There is constant communication between the Pakistan and US governments on this point, and between their military forces. The US is pursuing many of the terrorists that the Pakistani Government also wants dead. Pakistan's licence to rail at the US in public is a small price for the US to pay in order to keep on with the raids.

All the same, even if there has been a degree of complicity, it is clear that Pakistan's motives diverge sharply from the US's, and its tolerance will run out. At this point, with tension rising, and religious groups extending their support from the traditionally low level, Pakistan's leaders want a quiet life. They have, after all, been exploring deals with local Taleban for years, and even though that tactic has proved unable to stop the terrorism, it is still their preferred one.

Official warnings that Pakistan could turn its attention from the West to Kashmir should be taken seriously. Kashmir, not the western border, has been the army's historic preoccupation. President Pervez Musharraf's greatest achievement was to help to drain the heat out of the Kashmir issue by refocusing the army on the Western border. There is a risk that the army rediscovers its first love.

Particularly if it is given cause. This is a dangerous point. Talks with India have stalled in the past four years as Musharraf began fighting with the judiciary to cling to power, and as the Indian government, led by the Prime Minister Manmohan Singh and the Congress party, gave the problem fitful attention.

Barack Obama has rightly recognised the ability of Kashmir to unsettle India and Pakistan, and distract both from fighting terrorism. He has said that he wants to help to resolve it. India's traditional position is that outside intervention is unjustified and unwelcome; Kashmir, it says, is purely a bilateral dispute.

But at this point, that stance looks myopic. India is right to call for pressure on Pakistan - but that makes sense only if it is done in a way that recognises how fractured that country now is, and how its own urgent need for stability gives it different priorities from the West. One of the few things that India, and other countries, can help do is to move towards agreement over Kashmir. Obama is right that if it is not solved, this will be the cause of wider terrorism.

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