By Nick Childs
BBC News Pentagon Correspondent
The Pentagon has confirmed it is boosting troop numbers in Iraq by about 12,000. The reinforcement, it says, is temporary, but is to provide additional security in the run-up to the Iraq election scheduled for the end of January.
The Pentagon is worried about pre-election violence
It is perhaps a measure of the Pentagon's continuing concerns about the security situation in Iraq, and of how critical the planned election is, that US commanders have decided on this major troop increase.
US forces will go up from about 138,000 now to 150,000 at the time of the election - that will be the highest number yet, even more than actually invaded the country last year.
That in itself could reignite the debate over the planning for the post-war environment in Iraq and whether the current strategy for dealing with the insurgency is working.
Many in Congress have long argued that there haven't been enough US troops in Iraq.
The increase is mainly being achieved by asking thousands of US army soldiers and marines currently in Iraq to stay on longer than planned, even after their scheduled replacements arrive.
More than 8,000 troops from the 25th Infantry Division, the 1st Cavalry Division and a small transportation unit are being ordered to do this, as well as 2,300 personnel from the 31st Marine Expeditionary Unit.
They will stay on until about March.
Pentagon officials say this move underlines that it is not just a matter of numbers, but also of having experienced troops still on the ground in the country at what will be a critical time.
Still, the Pentagon is also sending further reinforcements in the shape of 1,500 troops from the army's crack 82nd Airborne Division.
A similar move, also involving troops from the 82nd Airborne Division, took place in Afghanistan in the run-up to the election there.
Clearly, US-led forces still have their hands full in the aftermath of the Falluja operation.
A statement from the US-led multinational command in Iraq said the troop increase was an attempt to keep the insurgents off-balance and to set the conditions for the election.
There is concern in the Pentagon the violence in Iraq could increase as the election approaches.
On top of this, though, the fact that thousands of US soldiers are now being asked to stay beyond the Pentagon's self-imposed limit of a 12-month tour of duty in Iraq could also provide new ammunition for those critics who argue the US military is being overstretched.