The Taliban have reportedly deployed 10,000 fighters for a spring offensive of "bloody attacks" against foreign troops in Afghanistan.
More than 4,000 people, a quarter of them civilians, were killed in fighting last year, the most violent year since the Taliban were ousted in 2001. NATO commanders and analysts warn this year could be just as bad or worse.
As the harsh winter snows melt, the insurgents have resumed their attacks, mostly in the south, where they have captured a major town and have threatened a key hydroelectric dam.
Mullah Abdul Rahim, the Taliban's operational commander for southern Helmand province - the opium center of the world's major producer - said militants would step up attacks in spring.
"As the weather becomes warm and leaves turn green, we will unleash bloody attacks on the U.S.-led foreign troops," Rahim told Reuters by satellite phone from a secret location.
"Our war preparations, especially in southern Afghanistan and in Helmand province, are complete and for this our 10,000 fighters are ready to take up arms the moment they are ordered."
Ater attempts at conventional pitched battles failed last year, the Taliban are expected to return to more conventional guerrilla tactics against government forces and the roughly 45,000 foreign soldiers in the country.
A key tactic is expected to be suicide bombings, which rose dramatically last year, killing more than 200 people, but which still remain much rarer than in Iraq. The Taliban say they have 2,000 suicide bombers ready and another 3,000 in training.
Rahim said the focus of attacks will be southern areas, where the Taliban was born.
Afghanistan's government says the militants are still sponsored by Pakistan, their main backer until September 11 attacks on the United States.
Islamabad concedes there is some border infiltration by the militants along the porous and largely lawless frontier, but denies supporting the rebels, who have ethnic roots on both sides of the British-drawn border. Pakistan says the insurgency is Afghanistan's problem.