Winter in Afghanistan is traditionally the season when hostilities cease, enforced hibernation sets in and the warring parties make preparations for the spring offensive.

But 2008 could be an exception. The first suicide bombing of the new year, an unprecedented attack against the Kabul Serena Hotel, has shaken the capital. The city is now braced for more bombings against Western civilian targets by the Taleban.

US forces have been in action this weekend against Taleban fighters in the east.

In the south five Afghan civilians were killed yesterday by a roadside bomb intended for a Nato patrol.

The bloody start to the year is probably a foretaste of what is likely to follow once the snows melt, the mountain passes reopen and the fierce struggle resumes for the fate of the country.

According to the Afghanistan NGO Safety Office, which advises aid groups on security in the country, Nato and the Taleban are about to enter a “broad and deep” conflict.

“In simple terms, the consensus amongst informed individuals at the end of 2007 seems to be that Afghanistan is at the beginning of a war, not the end of one,” the group said in a report looking ahead at 2008.

For the Taleban the strategy is clear. Spread the insurgency, undermine the reconstruction efforts, drive a wedge between foreign forces and the local population and isolate the beleaguered Government of President Karzai.

The movement is assisted by the chaos in neighbouring Pakistan. Men, arms and funds can more easily slip across the border, and its al-Qaeda allies, at large in the lawless tribal territories, are freer than at any time since 2001 to plan and execute operations across the border in Afghanistan.

The USled Nato forces, who have 40,000 troops in Afghanistan, are keenly aware of the growing threat and the need for more combat soldiers to meet the challenge, particularly in the lawless southern provinces.

But far from agreeing on a strategy, the alliance is dangerously divided. The main contributing nations remain at odds over who should do the fighting, for how long and the tactics employed.

The private differences broke out into a public row last week when Robert Gates, the US Defence Secretary, openly criticised the fighting skills of his main allies.

“I am worried we are deploying [military advisers] that are not properly trained and I am worried we have some military forces that do not know how to do counter-insurgency operations,” he told the Los Angeles Times.

“Most of the European forces, Nato forces, are not trained in counter-insurgency; they were trained for the Fulda Gap [Nato’s Cold War battle lines in Germany].”

The remarks triggered an angry response from Britain, the Netherlands, Canada, Australia and Denmark, whose troops have done the bulk of the fighting in southern Afghanistan. Mr Gates attempted to soothe offended allies, but did not withdraw his remarks.

At the heart of the frustration felt by the Pentagon is the failure of the European allies to commit more combat troops to the fight. Germany and Italy have refused to redeploy their forces from the relative safety of western and northern Afghanistan to the battlefields of the south.

Canada, whose forces have taken heavy casualties in the Taleban stronghold of Kandahar, has given warning that it may not extend its mandate beyond the end of this year because of growing public opposition to the war.

Nato commanders need 7,500 troops in Afghanistan and so far only America has stepped in to fill the gap with 3,200 Marines to fight alongside the 5,500 British forces in Helmand province.

Before Nato can hope to defeat the Taleban, it must resolve its internal conflict. The decisive battleground will likely be the Nato summit in Bucharest in April, when alliance leaders will have to recommit to the fight or face the prospect of defeat.

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