Gen. Peter J. Schoomaker's announcement represents an about-face by top Pentagon officials who have argued consistently that increasing the number of troops would drain money from new weapons programs and other modernization plans.

The announcement comes amid pressure from some in Congress who want to permanently add as many as 40,000 soldiers to the Army, which they say has been stretched too thin by the war in Iraq, deployment to Afghanistan, and other commitments around the world.

Schoomaker acknowledged in testimony to the House Armed Services Committee that the war on terrorism had put unprecedented strains on the Army, but he said it was too early to tell if these demands constituted a "spike or a plateau" in military operations.

He said Defense Secretary Donald H. Rumsfeld had given him emergency authority to "grow the Army" by as many as 30,000 soldiers using supplemental funds that Congress approved last year. He said it would take as long as four years and more than $3 billion to achieve that goal.

Schoomaker urged Congress not to increase the size of the Army permanently, arguing that such a move would undercut the Army's efforts to restructure its forces and modernize with new weapons and other technology. To add just 10,000 soldiers to the Army will cost $1.2 billion, he said.

"I am adamant that is not the way to go," he said.

Some of the increase will be achieved by transferring 10,000 jobs now performed by soldiers to civilians, freeing the soldiers for other duties, and by keeping soldiers in their positions longer, rather than moving them from one duty station to another every one or two years.

Schoomaker and the Marine Corps commandant, Gen. Michael W. Hagee, who also appeared before the committee, described the military's plans to replace 130,000 soldiers in Iraq with 105,000 fresh troops by spring. That effort constitutes one of the largest overseas troop rotations since World War II, said Rep. H. James Saxton (R., N.J.), the acting chairman.

Hagee said he agreed with Schoomaker that it was unclear if the war on terror would require a permanent increase in troops. The real question, Hagee said, is not about the number of troops in uniform but the capabilities those forces have.

"My concern is that three or four years from now the situation won't be the same," he said.

Schoomaker said the addition of 30,000 soldiers would add the equivalent of more than one heavy division to the Army, which stands at 10 active-duty divisions.

Schoomaker also said it would be counterproductive for the Army to add more soldiers while it was undergoing its biggest internal restructuring in 50 years, boosting its division structure from three brigades to four, and retraining some units such as field artillery into civil affairs, military police and intelligence specialties - the kind of postwar roles that are in high demand in Iraq.

With the ongoing war, how difficult will it be for the Army to increase by 30,000?