WASHINGTON - For planning purposes, the Army is gearing up to keep current troop levels in Iraq for another four years, a new indication that conditions there are too unstable to foresee an end to the war.

Defense Secretary Donald H. Rumsfeld, right, accompanied by Gen. George Casey , the top U.S. General in Iraq, gestures during a news conference at the Pentagon, Wednesday, Oct. 11, 2006. [AP]

Gen. Peter Schoomaker, the Army chief of staff, cautioned against reading too much into the planning, which is done far in advance to prepare the right mix of combat units for expected deployments. He noted that it is easier to scale back later if conditions allow, than to ramp up if they don't.

"This is not a prediction that things are going poorly or better," Schoomaker told reporters. "It's just that I have to have enough ammo in the magazine that I can continue to shoot as long as they want us to shoot."

Even so, his comments were the latest acknowledgment by Pentagon officials that a significant withdrawal of troops from Iraq is not likely in the immediate future. There are now 141,000 U.S. troops there.

At a Pentagon news conference, the top U.S. commander in Iraq, Gen. George Casey, said that as recently as July he had expected to be able to recommend a substantial reduction in U.S. forces by now. But that plan was dropped as sectarian violence in Baghdad escalated.

While arguing that progress is still being made toward unifying Iraq's fractured political rivalries and stabilizing the country, Casey also said the violence amounts to "a difficult situation that's likely to remain that way for some time."

He made no predictions of future U.S. troop reductions.

Appearing with Casey, Defense Secretary Donald H. Rumsfeld said he and other senior Pentagon officials are still studying how the military might keep up the current pace of Iraq deployments without overtaxing the Army and Marine Corps, which have borne the brunt of the conflict. Rumsfeld said one option is to make more use of the Air Force and Navy for work that normally is done by soldiers and Marines.

Sen. Jack Reed (news, bio, voting record), D-R.I., a member of the Senate Armed Services Committee, said Wednesday that the advance planning Schoomaker described was an appropriate cautionary approach. However, he added, the Pentagon should increase the overall size of the military to reduce stress on troops repeatedly sent into combat.

"I applaud the new realism but I think they also have to recognize that this (war) is going to put a huge stress on our forces," said Reed, a former Army Ranger. Reed and other Democrats have called on President Bush to start bringing home troops within a year to force the Iraqi government to take more responsibility for security.

At his news conference, Rumsfeld was asked whether he bears responsibility for what has gone wrong in Iraq or if the military commanders there are to blame.

"Of course I bear responsibility," he replied in apparent exasperation. "My Lord, I'm secretary of defense. Write it down."

In recent months the Army has shown signs of strain, as Pentagon officials have had to extend the Iraq deployments of two brigades to bolster security in Baghdad and allow units heading into the country to have at least one year at home before redeploying.

The Army is finding that the amount of time soldiers enjoy between Iraq tours has been shrinking this year. In the case of a brigade of the 3rd Infantry Division, its deployment to Iraq was delayed by about six weeks because it otherwise would have had only 11 months to prepare instead of the minimum 12 months. As a result, the unit it was going to replace has been forced to stay beyond its normal 12-month deployment.

In separate remarks to reporters, Gen. Richard Cody, the Army vice chief of staff, said soldiers need more than 12 months between deployments to Iraq so they can do a full range of combat training and complete the kinds of educational programs that enable the Army to grow a fully mature officer corps.

That kind of noncombat experience is necessary "so that we don't erode and become an Army that only can fight a counterinsurgency," Cody said. He added that North Korea's announced nuclear test "reminds us all that we may not just be in a counterinsurgency fight and we have to have full-spectrum capability."