The move comes after last month's announcement that thousands of U.S. troops would start being withdrawn later this year as part of a process of handing security over to Afghan forces.

"UK force levels in Afghanistan are kept under constant review," a Ministry of Defense spokesman said. "The prime minister (David Cameron) has been clear that there will be no UK troops in combat roles in Afghanistan by 2015 and it is right that we bring troops home sooner where progress allows and taking account of military advice."

The British government announced in May that it would pull about 400 troops from Afghanistan over the following nine months, trimming its force to 9,500.

Britain has the second-biggest foreign contingent in Afghanistan, with the majority in the southern Helmand province, one of the most violent areas. So far 374 British service personnel have died in the decade-long war.

Reuters