Maj. Gen. Eric Olson said he was concerned that American policy-makers will seize on an apparent drop in militant attacks to cut the 18,000-strong coalition — about 17,000 of whom are Americans — to ease the pressure on American forces stretched by their deployment in Iraq.
"The U.S. presence at the core of the coalition has been critical to success of the overall coalition effort," said Olson, the No. 2 U.S. commander in Afghanistan.
About 1,000 coalition troops are non-Americans, including a contingent of Egyptian medics, teams of French and Norwegian special forces, and a Romanian battalion in the southern city of Kandahar.
Olson said the operation is very taxing and there will be pressure to draw down forces while handing over more responsibility to what is now a 9,000-strong NATO security force.
"My fear is that will happen too fast, that the draw down will outrun the expansion or the compensation of NATO expansion," Olson said.
"I think there's still an insurgency to win here, and I think the Afghan central government is at this point very much dependent on the support of the coalition."
NATO plans to expand into western Afghanistan this year, then to the south, but the general said he was not convinced the alliance would match the numbers or capabilities of the U.S. units they eventually should replace.
He also said Afghanistan's new army and police would need five to 10 years before they could begin performing properly.
Olson reiterated that the trail of al Qaeda leader Osama bin Laden had "gone cold," but he said U.S. forces were continuing their search and he did not anticipate any letup in that part of their mission.
"There are no specific leads to bin Laden right now, but we collectively are just as determined to continue to hunt him," he said.
Olson spoke to the AP after visiting troops at three remote bases near the mountainous Pakistani border, where militants continue to undermine security.
Under Olson, who leaves Afghanistan next month, U.S. troops have set up several small bases across the country's south and east to back up officials from U.S.-backed President Hamid Karzai's government and to intercept militants crossing from Pakistan.
Commanders say that decision helped protect landmark October elections and has persuaded many ordinary Afghans to turn their back on the Taliban — gains Olson said could quickly be lost.
In a reminder of the country's insecurity, suspected Taliban insurgents launched three separate attacks on Thursday, reportedly killing nine Afghan troops and wounding an American soldier while sustaining heavy casualties themselves. Ten insurgents were killed.
The violence followed a period of relative calm in Afghanistan amid rising hopes that the insurgency is faltering. Taliban spokesmen have said attacks are down only because of the harsh winter, and they would resume once the weather improved.
An A-10 ground attack aircraft from Bagram Air Base, north of the capital, circled high over the snowcapped mountains surrounding one base as Olson handed out awards, including Bronze Stars, to troops from the Hawaii-based 25th Infantry Division.
Olson also praised Pakistan for a bloody crackdown on militants, including suspected al Qaeda fighters on their side of the border, but said they had "by no means" finished off forces with ambitions to retake Afghanistan.
"I honestly believe that (militant) pressure from Pakistan and a drawdown in Afghanistan would be an incredibly volatile combination," he said.
By Stephen Graham