Once again, the US must take the lead through a diplomatic minefield

The latest flare-up of the crisis between India and Pakistan over the disputed province of Kashmir not only threatens to undermine American-led efforts to uproot Islamic terrorism from southern Asia. It has brought the two nuclear-armed neighbours closer to full-scale war than at any time in three decades.

Every ingredient for tragedy is in place. Since the failure of the Agra summit of July 2001, what little trust existed between Delhi and Islamabad has evaporated. The domestic political weakness of both President Pervez Musharraf of Pakistan and Prime Minister Atal Bihari Vajpayee of India means that neither dares to give the impression of making concessions to the other side.

India, the proprietary power of the disputed southern portion of Kashmir, rejects Pakistan's call for foreign observers to police the Line of Control. Instead it demands that President Musharraf honours the undertaking he made in January to crack down on infiltration into Indian-controlled Kashmir by Islamic radicals based in Pakistan, who are accused of carrying out last week's raid on an Indian army camp which killed 34 people, many of them children and wives of soldiers on the front line. To underline its determination, Delhi has placed its paramilitary security forces in the region under the direct control of the army.

But President Musharraf, having taken the considerable risk of siding with America in its war against terrorism, dare not publicly yield to Indian pressure over Kashmir. Indeed, it is doubtful whether, even if he wanted to, he could halt incursions by the radical groups which, after the disruption of their former bases in Afghanistan, have merely relocated to sympathetic areas of Pakistan.

Thus a million men face each other across the border, ready for a war that neither side wants but the slightest miscalculation could detonate.

The case for urgent international diplomatic intervention is overwhelming – and, whether we like it or not, the US again must take the lead. For once, the diplomatic calendar is propitious. Indian defence officials are currently in Washington, while President Bush is about to hold a summit with President Vladimir Putin at which he will surely ask Russia, a traditional friend of India from Cold War times, to lean on its old ally to show restraint.

In the meantime, a mooted trip to the subcontinent by Richard Armitage, the Deputy Secretary of State, should go ahead without delay. True, his mission could prove as thankless as the one undertaken to the Middle East last month by his boss, Colin Powell. But America does have some useful cards to play, despite the historic aversion of India to foreign involvement in Kashmir. The first card is simple self-interest. The last thing the US and its allies want is a distraction from the Afghan campaign; on the other hand, progress over Kashmir would reduce one combustible that is fuelling terrorism in the region.

Second, the US has better relations with both sides in the dispute than for many years. After decades of neglect, it is cultivating ties with India, while Pakistan's international respectability depends on loyal membership of the anti-terror coalition assembled by Washington. Last but not least, the physical presence in Pakistan of US forces sent there as part of the war against al-Qa'ida will make India think doubly carefully before launching military action. But overriding everything is the plain fact that Pakistan and India's nuclear arsenals make the alternative to diplomacy unthinkable.