LONDON: Britain plans to withdraw thousands of troops from Afghanistan next year, Defence Secretary Philip Hammond said on Sunday, as pressure mounts to end British involvement in the costly and unpopular war.

Some 500 troops are due to be repatriated by the end of this year, leaving around 9,000. Hammond said he expected thousands of those remaining to go home in 2013, but not the majority, indicating a maximum withdrawal of around 4,500 personnel.

All British combat personnel are due to be withdrawn by the end of 2014.

"I would expect it will be significant, which means thousands, not hundreds, but I would not expect it to be the majority," Hammond told the BBC, after being asked about troop withdrawals next year.

At least 424 British troops have been killed in Afghanistan since the 2001 U.S.-led military invasion, yet stability has remained elusive and violence high.

Meanwhile Britain, like other NATO members, has slashed its defence budget and cut troop numbers and equipment programmes in response to constrained finances.