British Prime Minister Gordon Brown has said the coming months would be critical in Afghanistan as the offensive against the Taliban continues.
Mr Brown was speaking in Kandahar after he met the Afgan President Hamid Karzai on an unannounced visit to the country.
He said Britain and the US needed to show determination to take on and weaken the Taliban.
Mr Brown added that the government of Afghanistan must also play a bigger part in the future.
This year, 100 British soldiers have been killed in the fiercest fighting of the eight-year-old war, fuelling opposition in Britain to the forces' involvement.
With 9,500 troops pledged, the British contingent is by far the biggest of Washington's NATO allies and especially this year has borne the brunt of non-US NATO casualties.
Mr Brown hopes a trained Afghan force will gradually be able to take control of security, allowing British and other Western forces to take a less prominent role.
The prime minister acknowledged it had been a hard year, but said he was more confident about the future because new troops were coming and Britain was adding helicopters and mine-resistant vehicles.
His overnight stay in a spartan room at Kandahar air base was the first time either he or predecessor Tony Blair had spent the night in a war zone.
On previous trips to Afghanistan and Iraq they had both flown in and out on the same day.
