The Army is planning for the possibility of keeping the current number of soldiers in Iraq -- well over 100,000 -- for four more years, the Army chief of staff said yesterday.

In an interview, Gen. Peter J. Schoomaker said the service is prepared for the "worst case" in terms of the required level of troops in Iraq. He said the number could be adjusted lower if called for by slowing the force rotation or by shortening tours of duty.

Schoomaker said commanders in Iraq and others in the chain of command will decide how many troops will be needed next year and beyond. His responsibility is to provide them, trained and equipped.

About 138,000 U.S. troops, including about 25,000 Marines, are stationed in Iraq.

"We're staying 18 months to two years ahead of ourselves" in planning which active-duty and National Guard and Reserve units will be provided to meet the commanders' needs, Schoomaker said.

The main active-duty combat units scheduled to go to Iraq in the coming year are the 101st Airborne Division, based at Fort Campbell, Ky., and the 4th Infantry Division from Fort Hood, Tex. Both divisions did one-year tours earlier in the war.

With the recent deployment of brigades from Georgia and Pennsylvania, the National Guard has seven combat brigades in Iraq -- the most of the entire war -- plus thousands of support troops.

Along with the Army Reserve and Marine Reserve, they account for about 40 percent of total U.S. forces there. Schoomaker said that will be scaled back next year to about 25 percent as newly expanded active-duty divisions such as the 101st Airborne enter the rotation.