Defense Secretary Philip Hammond said the change in thinking came after commanders said they were "surprised" by the extent to which troops could let Afghan forces take the lead, The Guardian reported Friday.
Britain has closed 52 of its military bases and checkpoints in Helmand province, Hammond said. Thirty-four are operational.
"I think there is a bit of a rethinking going on about how many troops we do actually need," Hammond told The Guardian. "There may be some scope for a little bit more flexibility on the way we draw down, and that is something commanders on the ground are looking at very actively."
Hammond said no decision has been made. However, The Guardian said the defense secretary's comments represent the first indication British officials may be considering accelerating troop withdrawal next year instead of 2014, when the British military effort in Helmand ends.
Five hundred British troops will be withdrawn by the end of this year, leaving 9,000 in Afghanistan.
"I think that the message I am getting clearly from the military is that it might be possible to draw down further troops in 2013," Hammond said. "Whereas six months ago the message coming from them was that we really need to hold on to everything we have got for as long as we possibly can. I think they are seeing potentially more flexibility in the situation."
Now that al-Qaida had been "eliminated" from Afghanistan, British lives should not be put at risk for nation-building, he said.
"I believe very clearly that if we are going to ask British troops to put themselves in the firing line, we can only do that to protect U.K. vital national security interests," Hammond said. "We can ask troops ... to help build a better Afghanistan, but we cannot ask them to expose themselves to risk for those tasks. We can only ask them to expose themselves to risk for Britain's national security, which is what they signed up to do."
Hammond said Britain's involvement in Helmand should be considered a success story, The Guardian said.
"The message for people back home is that over the years we have contained the threat to U.K. security, we have built the Afghan security forces to the point that they can take over that burden," he said. "We are confident we will leave in place a solution that will not look perfect ... but if it maintains the integrity of Afghanistan and stops the use of it for international terrorists, we have achieved our primary purpose."