Progress against the Taliban is "tangible yet fragile" with 2011 likely to see a tough fight, the senior UK commander in Afghanistan has warned.
Lt Gen James Bucknall said Isaf, the international coalition, was preparing to hunt down insurgents in "safe havens" where they would normally sit out harsh Afghan winters.
He said a US troop surge meant Isaf now had the resources to go after them.
British troops have been in Afghanistan since 2001 and 346 have died.
Speaking from Kabul via videolink, Lt Gen Bucknall told reporters: "We believe that we are making progress.
"We have arrested the insurgents' momentum across much of the country and we have reversed it in some key areas," he said.
"But while that progress is tangible it remains at this stage fragile and it is certainly not irreversible. I think we must expect 2011 to be a tough fight."
He added that Isaf would use the winter months to seek out insurgents in retreats in central Afghanistan, northern Helmand and Daykondi.
"We have got to deny the insurgents the traditional safe havens which they have harboured in during the winter months," he said.
"Very often we have lacked the reach and the legs and the resources to go after them in those areas.
"I think we can expect a mixture of conventional and special forces operations to continue to disrupt the insurgents in those areas in the winter months."
He went on to say that in recent months, special forces had been operating at a "relentless tempo".
"We have remarkable target-precision that is causing significant attrition to the insurgents' mid-level leadership," he said.
"We know that they are impacting on morale and supplies."