The expansion will be achieved by sending about 1,500 troops from the 82nd Airborne Division this month and by extending the combat tours of about 10,400 troops already in Iraq.
One unit, the 2nd Brigade of the 1st Cavalry Division, is being extended for the second time. Its soldiers originally were told they would be going home in November, but in October they got the news that they would remain until the Jan. 30 elections. Now they are being extended until March.
Brig. Gen. David Rodriquez, deputy operations director of the Joint Staff, told reporters that these moves would increase the size of the American force in Iraq from 138,000 today to about 150,000 by January.
That is the highest number of U.S. troops in Iraq since the invasion, he said. By May 2003, when President George W. Bush declared major combat operations over, there were about 148,000 U.S. troops in Iraq, he said.
In other developments:
Rodriguez listed these unit extensions:
About 4,400 troops of the 2nd Brigade of the 25th Infantry Division, which is operating in north-central Iraq, will stay until mid-March, instead of departing in early January. Those soldiers' home bases are mostly in Hawaii.
About 3,500 soldiers of the 2nd Brigade of the 1st Cavalry, will be extended until March. These are the soldiers who originally were told they would be leaving Iraq in November.
About 2,300 members of the 31st Marine Expeditionary Unit, based in Okinawa, Japan and in Hawaii, and California, will stay until mid-March instead of leaving in January.
About 160 soldiers of the 66th Transportation Company, based in Germany, was due to depart Iraq in early January but instead will stay until early March.
The 82nd Airborne is generally relied upon by the Army to keep one of its three brigades on short-notice alert year-round to deploy abroad in the event of a crisis. Shortly before the October elections in Afghanistan, about 600 members of the 82nd Airborne were sent there to strengthen security.
Military officials have said repeatedly in recent weeks that they were considering whether more American troops would be required to provide sufficient security before Iraqis vote.
The moves announced Wednesday are in line with expectations — a combination of holding some troops in Iraq longer than scheduled and sending some fresh forces from the United States.
Officials have said they were considering sending some elements of the 3rd Infantry to Iraq earlier than scheduled, as part of a force-bolstering plan. But Rodriguez said it was decided that no units will have their deployments accelerated as part of the pre-election security effort.
Security problems are most severe in the area north and west of Baghdad, as well as in the capital itself. Voter registration has not yet begun in the more unstable cities such as Fallujah and Ramadi, west of Baghdad.
Recently there also has been trouble in the northern city of Mosul. On Wednesday, U.S. soldiers traveling through Mosul on a mission to discuss the January election with Iraqis came under fire at a gasoline station, witnesses said. One U.S. soldier was wounded in the ensuing gunbattle.