Reed, who served in the Army with the 82nd Airborne, also said in an interview that it is becoming increasingly clear that Iraqi forces will not be capable of taking over from U.S. forces for five to 10 years.
Yesterday's extensions mark the third time that the military has ordered troops to serve in Iraq longer than they expected.
Such extensions at first provoked anguish among family members who had been counting the days until the return of their deployed soldiers. When the 3rd Infantry Division's tour was extended in the summer of 2003, it prompted widespread grumbling, with some soldiers criticizing Defense Secretary Donald H. Rumsfeld by name.
But as the extensions have become more common in Iraq, the troops, their wives and their children have become more accustomed to them.
One of the units affected by yesterday's move, the 2nd Brigade of the 1st Cavalry Division, based at Fort Hood, Tex., is being extended for the second time.
Originally sent to Baghdad for a 10-month tour, it had already been told that it would not leave in November but would stay until January. Now, it is being told to remain in Iraq for an additional 45 days.
The second major Army unit extended, the 2nd Brigade of the 25th Infantry Division, was supposed to go home to Hawaii in January but is being held in Iraq until March.
Rodriguez said he expects troop levels to return to the current level in March.
But he also noted that "the plan is flexible, and we can adjust."
Although he said there are no plans to accelerate the deployment of other units scheduled to go to Iraq next year, other officials said some work is already being done to prepare for the early movement of some units. For example, said one Army official, the 3rd Armored Cavalry Regiment -- which in March 2004 returned from Iraq to Fort Carson, Colo. -- was scheduled to head back to Iraq in March or April 2005 but has now been told it might be sent there in February, just after the scheduled elections.
Overall, the boost in troop levels and the continuing changes in U.S. plans for Iraq are likely to raise new concerns in Congress and elsewhere about whether the size of the Army is adequate, and also about the strain that the fighting in Iraq is placing on the military.
"The fact that we are increasing numbers, and the likelihood that the fighting will continue for a long time, highlights a fundamental problem: Our active-duty ground forces are much too small," said Eliot Cohen, a Johns Hopkins University strategy expert. "We should have begun expanding them some time ago."