The deployments would replace troops currently there. But the decisions could change depending on whether Gen. David Petraeus, the top U.S. commander in Iraq, decides in the fall to further reduce troop levels in Iraq.
Several officials familiar with the deployments spoke on condition of anonymity because the orders have not yet been made public.
According to the officials, three active-duty Army brigade combat teams, one Army National Guard brigade and two Marine regimental combat teams are being notified that they are being sent to Iraq in early 2009. Officials would not release the specific units involved because the soldiers and Marines and their families have not all been told.
The Guard unit, however, is the 56th Brigade Combat Team, 28th Infantry Division, from the Pennsylvania National Guard. Members of that unit - a large brigade with heavily armored Stryker vehicles - were told last October that they should be prepared to deploy to Iraq early in 2009. The order this week is the formal notice that includes a more specific time frame.
Currently, the final brigade involved in the military buildup in Baghdad last year is pulling out of Iraq. That departure will leave 15 combat brigades there - compared to a high of 20 for much of the past year. Other smaller units are also there, including troops doing security, logistics, air assaults, intelligence and medical aid.
Overall, there are about 146,000 forces in Iraq, and that number is expected to dip to about 142,000 by mid-July when that last unit is all out. That total is at least 7,000 more than the number of troops in Iraq before the buildup began early last year.
Petraeus told Congress in May that he is likely to recommend further troop reductions in Iraq, but he did not provide any details. If he decides in the fall that fewer brigades will be needed in Iraq during the next year, there is the chance that brigades could simply be directed to the war in Afghanistan instead.
There is a broad consensus that more troops are needed in Afghanistan, to both train the security forces and fight the insurgents. Defense Secretary Robert Gates and President Bush, earlier this year, told NATO allies that they would increase troop levels in Afghanistan in 2009 in response to the growing violence.