British forces could begin pulling out of Iraq by next March, a senior defence source has revealed to the BBC.
The UK has been negotiating the legal basis on which its forces can stay when its UN mandate expires at the end of the year.
It still has 4,100 troops in Basra but defence chiefs plan a withdrawal over the next year if Iraqi elections in January pass off peacefully.
A withdrawal could allow soldiers to be diverted to Afghanistan.
Prime Minister Gordon Brown has indicated that almost all British troops should leave Iraq by the middle of next year, with a few hundred possibly remaining to train Iraqi security forces.