The head of the United Nations mission in Afghanistan has said that there is no quick military fix to end the insurgency in the troubled country, the Guardian reported on Saturday.
Tom Koenigs, the German diplomat who is the senior UN envoy there, said that instability would not be resolved by "killing Taliban", the paper said.
"We have a limited window to act. Otherwise they will chase us out within three years," he told the paper.
The Guardian said his comments highlighted divisions between international partners as NATO, which took control of military operations in Afghanistan in October, battles fierce resistance.
They come ahead of an impending meeting in Pakistan between British Prime Minister Tony Blair and President Pervez Musharraf, allies in the US-led "war on terror" which precipitated the 2001 invasion, to discuss the insurgency.
Koenigs reportedly sounded a note of caution over NATO's assessment of how they can overcome the problem.
"At the moment, NATO has a very optimistic assessment and they think they can win the war... They say development can follow military action.
"But there is no quick fix," he told the paper.
Koenigs added that the military alliance should "stop doing things on their own" and cited the involvement of the Afghan National Army (ANA) as crucial to future stability.
"They (the ANA) can win. But against an insurgency like that, international troops cannot win," the paper quoted him as saying.
"You can't resolve this by killing Taliban.
"You have to win people over. And that is done with good governance, decent police, diplomacy with Pakistan and development."