Gates made the remark to reporters in advance of a NATO meeting at which he said he would be raising the issue of how to pay for a planned doubling in the size of the Afghan national army. He called the building up of the Afghan army the ultimate exit strategy for both the U.S. and its allies.
Gates was not explicit about the nature of the U.S. strategy review. When pressed by reporters, he would say only that the administration is "looking at" the current strategy.
On Wednesday, Gates expressed "personal regret" for recent U.S. airstrikes that killed Afghan civilians, and pledged more accurate targeting in future.
Gates' unusual apology was evidence of what a major point of contention civilian casualties have become with the Afghan government, reported CBS News national security correspondent David Martin.
The civilian casualties also point to a fundamental problem facing the U.S. in Afghanistan - not enough troops. The shortage forces commanders to rely on air strikes in going after the Taliban and al Qaeda, and air strikes invariably produce civilian casualties.
After meeting with Afghan President Hamid Karzai and other senior government officials, Gates said at a news conference, "As I told them, I offer all Afghans my sincere condolences and personal regret for the recent loss of innocent life as a result of coalition airstrikes."
Also this week, the commander in Afghanistan, Gen. David McKiernan, said he needed a total of four more combat brigades - roughly 15,000 troops - in order to cover the terrain. One of those brigades is due to arrive in January, a second could get there in May, but it will depend on further withdrawals from Iraq, Martin reported.
It could be 2010 before the fourth brigade gets there, so the problem of not enough troops is not going to be solved any time soon.