WASHINGTON — The United States won't be sending more combat troops to Afghanistan despite Canada's demand for NATO reinforcements as a condition for staying in the battle, a U.S. Defence Department spokesman said Tuesday.

Pentagon spokesman Geoff Morrell told a briefing that the deployment of 3,200 American marines announced earlier this month is the limit for now.

Just over two-thirds of them, 2,200, are scheduled to arrive in March in the dangerous region in southern Afghanistan.

"That's as much and as deep as we're going at this point,'' said Morrell.

"We've got a number of allies with us there. And hopefully they can see to it to dig deeper and find additional forces to help this effort,'' he said.

"Hopefully, we'll make some progress there that will help the Canadians extend their commitment to the mission.''

U.S. Defence Secretary Roberts Gates hasn't talked to Canadian Defence Minister Peter MacKay since John Manley's commission report on Afghanistan was released last week, said Morrell.

Prime Minister Stephen Harper has endorsed the report's chief recommendation -- that Canada stay in Afghanistan for the duration of the war as long as NATO provides a modest increase of 1,000 soldiers for Kandahar.

Canada is also demanding more battlefield helicopters and surveillance aircraft.

About 2,500 Canadian troops are involved in the Afghan mission, most of them operating in Kandahar province.