The document being drawn up by the British government and the US will be presented to the Iraqi parliament in October and will spark fresh controversy over how long British troops will stay in the country. Tony Blair hopes that, despite continuing and widespread violence in Iraq, the move will show that there is progress following the conflict of 2003.

Britain has already privately informed Japan – which also has troops in Iraq – of its plans to begin withdrawing from southern Iraq in May, a move that officials in Tokyo say would make it impossible for their own 550 soldiers to remain.

Speaking to The Observer this weekend, the Defence Secretary, John Reid, insisted that the agreement being drawn up with Iraqi officials was contingent on the continuing political process, although he said he was still optimistic British troops would begin returning home by early summer.

For Blair, the question of withdrawal is one of the most difficult he is facing. The Prime Minister has abandoned plans, announced last February, to publish his own exit strategy setting out the milestones which would have to be met before quitting: instead, the plans are now being negotiated between a commission representing the Shia-dominated Iraqi government, and senior US and UK diplomats and military commanders in Baghdad.

Senior military sources have told The Observer that the document will lay out a point-by-point ‘road map’ for military disengagement by multinational forces, the first steps of which could be put in place soon after December’s nationwide elections.

Each stage of the withdrawal would be locally judged on regional improvements in stability, with units being withdrawn as Iraqi units are deemed capable of taking over. Officials familiar with the negotiations said that conditions for withdrawal would not demand a complete cessation of insurgent violence, or the end of al-Qaeda atrocities.

Isn’t it amazing how the approach of election time — in Britain or the US — can affect military policy? Or, at least, what our governments tell us about military policy.