CAMP LEATHERNECK, Afghanistan — American military officers tell The Associated Press that U.S. Marines will march out of Afghanistan by the thousands next year, winding down combat in the Taliban heartland.

The move also will test the view that Afghan forces are capable of leading the fight against a battered but not yet beaten insurgency in the country's southwestern reaches.

At the same time, U.S. reinforcements will be sent to eastern Afghanistan in a bid to reverse recent gains by insurgents targeting Kabul, Afghanistan's capital.

The commandant of the Marine Corps, Gen. James F. Amos, tells the AP that the number of Marines in Helmand province will drop "markedly" in 2012, while the role of those who stay will shift from countering the insurgency to training and advising the Afghan security forces.