Britain has said it wants to pull the bulk of its 9,500-strong force out of the war zone within five years, in line with an international aspiration to give Afghans full control of their security by the end of 2014.
The United States, which has committed the bulk of foreign troops deployed in Afghanistan, hopes to start bringing soldiers home from July 2011.
Asked in an interview with BBC Radio 5 Live whether Britain could match that, Cameron said, “Yes, we can but it should be based on the conditions on the ground.”
“I mean, the faster we can transition districts and provinces to Afghan control, clearly the faster that some forces can be brought home,” he said.
“I don’t want to raise expectations about that because that transition should be based on how well the security situation is progressing.”
The new premier, in charge of a Conservative-Liberal Democratic coalition that took power in May, said the British public should be clear that, by 2015, the UK would not have “combat troops or large numbers” in Afghanistan.