As it mobilizes for an Afghanistan troop buildup, the US Army will have to delay plans to allow war-weary soldiers more time at home between combat tours, the chief military officer said Thursday.

Admiral Mike Mullen acknowledged that while the Marine Corps will reach in 2010 the Pentagon's goal of increasing "dwell time" to two years at home for every year deployed, "it'll take a couple more years to do that" for the army.

Senior commanders have struggled to ease the strain on the army and the marines amid rising rates of depression, divorce and suicide believed to be fueled by repeated deployments.

Veterans groups have pushed the administration to expand dwell time and Pentagon studies have shown that soldiers who spend more time at home between deployments report fewer mental health problems.

To meet the demands of two wars and reduce pressure on the all-volunteer force, the Pentagon has expanded the size of the Marines Corps and the Army.

In July, Defense Secretary Robert Gates announced a temporary expansion of the army by 22,000 to ensure units were fully manned. Before the move, the service branch had grown to 547,000 active-duty soldiers.