Defence Correspondent, BBC News
The US has warned that gains in Afghanistan could slip away
The recent attempts by the US to urge its allies to boost their combat roles in southern Afghanistan has both puzzled and antagonised some Nato members, who see it as unconstructive and driven mainly by America's domestic politics.
In a rather testy answer to US Defence Secretary Robert Gates' demands for more combat troops, Germany has made it clear it is doing all it can in northern Afghanistan.
In his response, the German defence minister reminded America that the mandate for its 3,200 troops was set by the country's parliament last year, so could not be changed.
America feels that it is bearing the brunt of the fighting in the south, and is sending in another 3,000 marines to reinforce its operations there - leaving Mr Gates and the US administration having to explain to the American public why other Nato allies are not doing the same.
Recently, Mr Gates also antagonised some Nato partners who are taking part in combat operations in the south by criticising their ability to fight the insurgency.
Nato's Secretary General Jaap de Hoop Scheffer has made it clear he finds such public demands by the US unhelpful.
"I think force generation, as we call it - bringing the forces together for Afghanistan - is a Nato responsibility," he told the BBC in an interview. "I'm concerned, because I think this is obscuring the good things happening in Afghanistan and the success the mission is having."
Yet America's outspoken calls for more troops to share the burden highlights growing worries about the situation in Afghanistan.
Three separate reports published on Thursday warned that the country was in danger of sliding backwards without a renewed international effort.
Canada will not renew its mission without more Nato support
The blocking by Afghan President Hamid Karzai of the nomination of British peer Lord Ashdown as the new UN envoy to Kabul has led to fears of a rift between the Afghan government and the international community.
There is little doubt that a strong personality, trusted by all sides, will be vital in that role if the UN envoy is to bring together the disparate and sometimes unco-ordinated military and civil reconstruction efforts in a nation whose people and infrastructure have been battered by 30 years of war.
Britain has thus far stayed out of the latest public discussions over troop contributions, preferring to keep its thoughts for the Nato defence ministers' meeting in Vilnius next week.
Although with 7,800 troops of its own fighting in southern Afghanistan, Britain remains keen that other nations play their part there as well.
Prime Minister Gordon Brown has also emphasised the need for closer co-ordination between the military campaign and political and economic development in Afghanistan, with a renewed focus on reconstruction and winning over the lower level of Taleban fighters as a vital part of defeating the insurgency.
So just how bad are the splits within Nato over Afghanistan?
Perhaps not quite as bad as they currently appear. Nato is not yet winning in Afghanistan, but nor is it losing.
Though more troops are undoubtedly needed, the 42,000 already there give the alliance a huge military advantage which has forced the Taleban to resort to other tactics such as suicide bombings.
The bombing campaign remains a real threat to the civilian population in Afghanistan, but at the same time it could backfire as a tactic, as it may well diminish Afghan support for the insurgency.
And while Mr Gates' interventions may have angered some Nato allies, they are also a sign that America remains engaged in Afghanistan and determined for the mission to succeed.
US Secretary of State Condoleezza Rice is travelling to London next week for talks after her spokesman warned that there was a risk that "the clock could be turned back on the gains" made since the Taleban regime in Afghanistan was toppled in 2001.
Nato's members know they cannot afford to fail now. All sides are aware that stabilising Afghanistan is the mission Nato has staked its reputation on.
That means that the alliance will have to pull together rapidly, for the sake of its own credibility as well as for the future of Afghanistan, whose people are rapidly losing faith in the ability of their own government and the international community to improve their daily lives.