British Prime Minister Gordon Brown has arrived in Afghanistan on an unannounced visit, vowing a renewed effort to defeat the Taliban insurgency.
He says the next few months are critical.
Mr Brown's comments come two weeks after he ordered 500 extra British soldiers into the war alongside a surge of 30,000 American troops.
The troops are being deployed as part of a sweeping new United States strategy to turn around the eight-year war.
Mr Brown has held talks with Afghanistan President Hamid Karzai at a military base in Kandahar, the southern province where the Taliban originated.