The proposal went to Gates on Friday, and while he told reporters that afternoon that he had some questions about the move, there has been every indication he was poised to approve it.

According to officials, 2,200 members of the 24th Marine Expeditionary Unit, based at Camp Lejeune, N.C., will go to Afghanistan, as well as about 1,000 members of the 2nd Battalion, 7th Marine Regiment, which is based at Twentynine Palms, Calif.

The officials spoke on condition of anonymity because the deployment announcement has not yet been made. If approved, the deployment to southern Afghanistan would be a "one-time, seven-month" assignment, Pentagon Press Secretary Geoff Morrell said Friday.

The 2nd Battalion, which is from the Marine Corps Air Ground Combat Center, is an infantry unit, and it will be used largely for training Afghan forces.

The decision to increase U.S. troop levels in Afghanistan represents a shift in Pentagon thinking that has been slowly developing in recent months. Commanders faced with increasing violence have said they need as many as 7,500 more troops, but Gates initially pressed for other NATO nations to fill the void.

NATO countries, however, faced public opposition to deeper involvement there and were slow to respond, leaving Gates to acknowledge recently that the U.S. may have to consider providing the extra combat troops.

Currently, there are about 27,000 U.S. troops in Afghanistan, including 14,000 with the NATO-led coalition. The other 13,000 U.S. troops are training Afghan forces and hunting al-Qaida terrorists.

Afghanistan Defense Ministry spokesman Gen. Mohammed Zahir Azimi said last week that the deployment would help combat Taliban insurgents. But Azimi added the long-term solution was to boost the fighting strength of Afghanistan´s own army.