Leading article: The perils of failure in Afghanistan

The next US Vice-President, Joe Biden, was in Kabul yesterday for talks with the Afghan President, Hamid Karzai, and the commander of Nato-led forces in the country, General David McKiernan. General McKiernan is demanding more troops and equipment from the US and other Nato countries. He seems likely to be successful because Barack Obama has made it clear that stabilising Afghanistan is one of his administration's key foreign policy objectives.

This is the right priority for the incoming US President. Before the toppling of the Taliban in 2001, Afghanistan was a safe haven for extremists and international terror groups. Unless the country is stabilised, it will become one again. That would be a disaster both for the West and the Afghan people. But we must be in no doubt what a perilous and difficult job it will be for the international community to put Afghanistan back on the right track. Militarily, the Taliban is anything but beaten. Even before yesterday's death of a Royal Marine, there has been a high casualty toll among British troops stationed in Helmand province this winter. This is ominous because winter is supposed to be the quiet season. There is every reason to expect more serious fighting over the coming year.

Greater military resources to put down the threat and protect vulnerable villages are necessary, and yet force can only be one part of the strategy. Diplomatic pressure will be needed too. The only long-term solution to Afghanistan's instability can be a regional one. As long as the Taliban is able to flit across the border to Pakistan it will prove impossible to defeat. Pakistan needs to better police its western frontier.

On the political front, the allegations of corruption that circle President Karzai's administration make matters vastly more complicated. It would be fatal for Nato forces to be seen as propping up a corrupt regime. Unless President Karzai takes action to root out venal ministers, the whole game could easily be lost.

Hope for Afghanistan is still not extinguished, but only a sustained and intelligent effort on all fronts by the new US administration and its allies, including Britain, can prevent the light going out for good.