The next U.S. president and government will have to make any decisions on a sizable troop increase for combat operations in Afghanistan, a spokesman for the Pentagon said Wednesday.

U.S. commanders in the nearly seven-year-old war have been asking for three combat brigades, or roughly 10,000 more troops, to help confront increasing violence in Afghanistan. In addition to current troop strength, that would mean about 50,000 U.S. soldiers, marines, sailors and airmen in Afghanistan.

Defence Secretary Robert Gates said last week that officials have been looking for ways to send additional forces as soon as possible — likely in smaller units and fewer numbers than field commanders have requested.

But U.S. Defence Department press secretary Geoff Morrell told a news conference Wednesday that the decision on how and when to meet the request for the larger amount is "a question, frankly, for the next administration," which will be chosen in November's presidential election.

His comment came as U.S. President George W. Bush was arriving at the Pentagon for a briefing by top military leaders.

Bush has made the five-year-old war in Iraq the Pentagon's top priority, and U.S. military officials have been candid about the fact that the focus on Iraq has meant fewer troops and other military assets available for the campaign in Afghanistan.

"That is the war which we have focused on," Morrell said of Iraq. "That is the war we are now winning."

Pentagon officials have said that if improved security conditions in Iraq hold, they hope to be able to devote more troops to Afghanistan, where resurgent Taliban militants have been increasing their attacks in all parts of the country.

That includes Kandahar, where most of Canada's 2,500 troops are deployed.