Defense Secretary Donald Rumsfeld has signed off on a plan to boost U.S. troop levels in Iraq by 10,400 before scheduled elections take place Jan. 30, according to military sources.

The reinforcements will increase the force size in Iraq to approximately 150,000 personnel — the highest level of the war. The previous high was 148,000 on May 1, 2003, when President Bush declared that major combat operations were over.

Units being sent to Iraq will include two battalions, or about 1,500 soldiers, of the 82nd Airborne Division (search), based at Fort Bragg, N.C.

The 82nd Airborne sent about the same number of troops to Afghanistan as a demonstration of beefed-up security before that country's elections in October. These paratroopers, who are trained to start deployments within 18 hours of receiving their orders, are expected to be deployed for four months.

The division constantly keeps one of its three brigades on alert so that it can deploy abroad quickly in the event of a crisis.

Meanwhile, other troops will have their duty times extended.

The 10,400 number includes roughly 6,500 already planned — some 3,500 troops from the 1st Cavalry Division, as well as about 3,000 troops from the 1st Infantry Division. Their stays, which were in the 10- to 12-month range, have been extended two months.

About 2,300 troops from the 31st Marine Expeditionary unit from Okinawa, Japan, as well as several Kuwait-based transportation units, will also be held longer to facilitate new troop movements. Meanwhile, 4,400 troops from the 2nd Brigade of the 25th Infantry Division from Schofield Barracks, Hawaii, have had their tours extended two months; estimated time of departure is now mid-March.

And 3,300 troops from the 2nd Brigade of the 1st Cavalry Division at Ft. Hood, Texas, also has been "double-extended," meaning they had two months tacked on to their original 12 months, and now have had another two months added to that. Total time in theater for this group will be 14 months. Estimated time of departure is now mid-March. And 160 troops from the 66th Transport Co., from Kleber Kasern, Germany, also will have their tours extended by about 120 days.

This extension, combined with the current force rotation, will increase the U.S. forces in theater from 17 to 20 brigades.

Members of the two 82nd Airborne battalions, and their families, were told of the decision Tuesday, an Army official said.

The battalions were given what the Army calls a "warning order," alerting them that they will be moving out.

A battalion generally numbers about 500 to 600 soldiers.

Military officials said repeatedly in recent weeks that they were considering whether more American troops would be needed to provide security before the election.

Sources said Gen. George Casey (search), commander of coalition forces in Iraq, made the troop request directly to Rumsfeld.

Casey and Pentagon officials believe the success in cleaning out enemy fighters in Fallujah has given the coalition significant momentum heading into the elections, and want to maintain the leverage they believe the coalition now has over the insurgents.

"This provides an image of security, and shows how we wish to extend our cooperation with the interim government," an Army official said late Wednesday morning.

As recently as Tuesday, Gen. Richard Myers (search), chairman of the Joint Chiefs of Staff, said commanders in Iraq were still studying troop requirements ahead of the election.

He was quoted by the Pentagon's internal news service as saying in Indianapolis that the number of troops needed was "to be determined."

The moves 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.

The United States is in the midst of swapping out units that have been there for a full year with fresh forces, including the 3rd Infantry Division (search), which helped spearhead the original invasion in the spring of 2003.

Officials said they were considering sending some elements of the 3rd Infantry to Iraq earlier than scheduled as part of a force-bolstering plan. It was not clear Wednesday if that had been decided, but some officials suggested the scenario was unlikely.

Security problems are most severe in the so-called Sunni Triangle (search) 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.

Since the Fallujah operation began, insurgent attacks have moved to the northern city of Mosul.

On Wednesday, U.S. soldiers traveling through Mosul on a mission to discuss the elections with Iraqis came under fire at a gas station, witnesses said. One U.S. soldier was wounded in the ensuing gunbattle.

FOX News' Bret Baier and Ian McCaleb and The Associated Press contributed to this report.