WASHINGTON - The Pentagon has abandoned its limit on the time a citizen-soldier can be required to serve on active duty, officials said Thursday, a major change that reflects an Army stretched thin by longer-than-expected combat in Iraq. The day after President Bush announced his plan for a deeper U.S. military commitment in Iraq, Gen. Peter Pace, chairman of the Joint Chiefs of Staff, told reporters the change in reserve policy would have been made anyway because active-duty troops already were getting too little time between their combat tours. The Pentagon also announced it is proposing to Congress that the size of the Army be increased by 65,000, to 547,000 and that the Marine Corps, the smallest of the services, grow by 27,000, to 202,000, over the next five years. No cost estimate was provided, but officials said it would be at least several billion dollars. Until now, the Pentagon's policy on the Guard or Reserve was that members' cumulative time on active duty for the Iraq or Afghan wars could not exceed 24 months. That cumulative limit is now lifted; the remaining limit is on the length of any single mobilization, which may not exceed 24 consecutive months, Pace said. In other words, a citizen-soldier could be mobilized for a 24-month stretch in Iraq or Afghanistan, then demobilized and allowed to return to civilian life, only to be mobilized a second time for as much as an additional 24 months. In practice, Pace said, the Pentagon intends to limit all future mobilizations to 12 months. Members of the Guard combat brigades that have served in Iraq in recent years spent 18 months on active duty — about six months in pre-deployment training in the United States, followed by about 12 months in Iraq. Under the old policy, they could not be sent back to Iraq because their cumulative time on active duty would exceed 24 months. Now that cumulative limit has been lifted, giving the Pentagon more flexibility. The new approach, Pace said, is to squeeze the training, deployment and demobilization into a maximum of 12 months. He called that a "significant planning factor" for Guard and Reserve members and their families. David Chu, the Pentagon's chief of personnel, said in an interview that he thinks Guard and Reserve members will be cheered by the decision to limit future mobilizations to 12 months. The fact that some with previous Iraq experience will end up spending more than 24 months on active duty is "no big deal," Chu said, because it has been "implicitly understood" by most that they eventually would go beyond 24 months. A senior U.S. military official who briefed reporters Thursday on Iraq-related developments said that by next January, the Pentagon "probably will be calling again" on National Guard combat brigades that previously served yearlong tours in Iraq. Under Pentagon ground rules, the official could not be further identified. Defense Secretary Robert Gates, appearing with Pace, announced several other changes in Guard and Reserve policy: _Although the Pentagon's goal is to mobilize Guard and Reserve units no more frequently than one year out of six, the demands of wartime will require calling up some units more often than that. They provided no details on how many units would be remobilized at the faster pace or when that would begin to happen. Army officials had been saying for some time that more frequent mobilizations were necessary because the active-duty force is being stretched too thin. Gates' announcement is the first confirmation of the change. _To allow for more cohesion among Guard and Reserve units sent into combat, they will be deployed as whole units, rather than as partial units or as individuals plugged into a unit they do not normally train with. _Extra pay will be provided for Guard and Reserve troops who are required to mobilize more than once in six years; active-duty troops who get less than two years between overseas deployments also will get extra pay. Details were not provided. _Military commanders will review their administration of a hardship waiver program "to ensure that they have properly taken into account exceptional circumstances facing military families of deployed service members." As part of Bush's plan for boosting U.S. troop strength in Iraq, a brigade of National Guard soldiers from Minnesota will have its yearlong tour in Iraq extended by 125 days, to the end of July, and a Patriot missile battalion will be sent to the Persian Gulf next month, the Army said Thursday. Maj. Randy Taylor, a spokesman for the 3rd Battalion, 43rd Air Defense Artillery Regiment, at Fort Bliss, Texas, said the Patriot unit was aware of the announced deployment. He said no formal order had been received Thursday. The dispatching of a Patriot missile battery, capable of defending against shorter-range ballistic missile attacks, appeared linked to Bush's announcement Wednesday that he ordered an aircraft carrier strike group to the Middle East, which would be in easy reach of Iran, whose nuclear program is a U.S. concern. Navy officials said the carrier heading to the Gulf region is the USS John C. Stennis, which previously had been in line to deploy to the Pacific. It was not clear Thursday how the Pentagon intended to compensate in the Pacific for the absence of the Stennis in that region, where a chief worry is North Korea. The Marines announced that two infantry units — the 3rd Battalion, 4th Marine Regiment, and the 1st Battalion, 6th Marine Regiment — will stay in Iraq 60 to 90 days longer than scheduled. That will enable the Marines to have a total of eight infantry battalions in western Anbar province, instead of the current six, by February. Once the 60- to 90-day extension is over, an additional two battalions will be sent in early from their U.S. bases. Also, the 15th Marine Expeditionary Unit, which combines infantry with a helicopter squadron and a logistics battalion, totaling about 2,200 Marines, will stay in Anbar for 45 more days. Those extensions conform with Bush's announcement that he was ordering 4,000 more Marines to Anbar. The military tries to avoid extending combat tours and sending forces earlier than planned because it disrupts the lives of troops and their families and makes it harder for the services to get all troops through the education and training programs they need for promotions. But in this case it was deemed unavoidable.