NATO forces are scheduled to hand over the security of Afghanistan to its own forces by 2014.
However, Gen. James Bucknall, commander of the British forces in Afghanistan and now the second in command of NATO forces, told Britain's Guardian newspaper without an assurance to Afghanistan, the Taliban would be emboldened, adding "now is not the time to blink" as there has been progress in the 10-year war.
The report said there is already concern in Kabul about NATO's plans to draw down its forces later this year and U.S. policy in the aftermath of the killing of al-Qaida leader Osama bin Laden.
"Afghanistan has been the center of the world for the past 10 years," one diplomatic source told the Guardian. "It isn't anymore and the purse strings from donors will soon tighten. The international military drawdown will begin … After this, many Afghans fear they will then be abandoned again."
Bucknall warned the Taliban would "come back at us as hard as they can" this summer and that the insurgency would not have ended by the end of 2014, the report said.
He said until the West has makes it "clear that the international community is not going to abandon Afghanistan in the near term, until that time, the insurgents will think that they can wait out the campaign.
"The Afghan people will not necessarily have the confidence to back their own government. And it is important that the regional players understand that the international community is going to be here for some time to come," the general said.