Defence Secretary Philip Hammond said the real progress being made in Helmand Province will "allow us to reduce British troops to 5,200 by end of 2013."
Mr Hammond said:
There will not be a cliff edge reduction in troop numbers at the end of 2014. This gradual drawdown in line with ISAF planning.
A Conservative backbencher has said that the government's decision to withdraw troops from Afghanistan will be "difficult and dangerous".
ITV News understands that Britain's withdrawal from Afghanistan may be speeded up with troop numbers almost halved in the next year.