More troops are needed to cope with the strain of two wars
US military chiefs have approved a proposal to speed up the expansion of the US Army.
A total of 74,000 soldiers will be added by 2010, rather than 2012 as originally planned.
The plan follows fears the US Army is being stretched to breaking point by the wars in Iraq and Afghanistan.
The announcement comes amid reports that the US Marines are planning to leave Iraq and focus their operations in Afghanistan because of troop strain.
The acceleration in army expansion was approved by US Secretary of Defense Robert Gates in September.
The plan would take the number of soldiers in the army, army guard and army reserve to 547,000.
The troop increases will cost $2.63bn (£1.1bn) and will be partly achieved by persuading existing soldiers to stay on in the army longer than planned.
There will also be a scheme to give bonuses of $2,000 (£980) per recruit to any National Guard soldier who persuades somebody to join the regular army.
Reduction in quality?
"Meeting this target will not be easy," said Gen George Casey. "It will require a total force effort if we're going to expand more rapidly and maintain the quality [of the troops]."
The army has been criticised in recent years for failing to meet its own targets for troop quality.
Only 79% of new recruits have graduated from high school, short of the 90% target.
And the proportion of 2007 recruits that required a waiver because they did not meet moral, medical or aptitude standards rose to 18% from 15% in 2006.
US ARMY EXPANSION
Regular troop levels will increase by 65,000 to 547,000 by 2010
Reserve troop levels will rise by 9,000
The expansion will cost $2.63bn (£1.1bn)
The reported plan to move the US Marine Corp from Iraq to Afghanistan would also help to reduce strains on the US military.
It would allow the army to move units out of Afghanistan and into Iraq, enabling both the army and the marines to operate more efficiently, according to senior officials quoted in the New York Times.
The US marines do not currently have a presence among the 26,000 US troops in Afghanistan.
There are 25,000 marines among the 160,000 American troops in Iraq, however.