ANCHORAGE, Alaska (AP) _ About 26,000 troops, 120 aircraft and 1,000 vehicles from Canada and the United States began maneuvers across Alaska in the military's regular test of personnel and machines in freezing temperatures.

''This may be the premier cold-weather exercise in the Free World,'' Air Force Lt. Gen. Thomas G. McInerney, commander of Joint Task Force-Alaska, said Friday as the biennal exercise began Friday.

''Brim Frost '89'' - a $15 million training exercise involving the U.S. Army, Air Force, Marines, Coast Guard, National Guard, reserve units and the Canadian Forces - is to continue through Feb. 1.

''We hold some exercises like this in Norway, but they're a little different,'' McInerney said. ''Here you have an entire (Army) division operating in an arctic environment.''

Maneuvers were planned at more than 17 sites around Alaska, including Kodiak Island in the Pacific Ocean, but the focus will be a major land battle between two Army brigades on the Tanana Flats at Fort Greely, about 75 miles southeast of Fairbanks.

That will include a battalion-sized Canadian force dropped by parachute, officials said.

''It will be a rehearsal of the procedures we'd have to go through if we actually had to defend Alaska,'' said Army Maj. Gen. Harold T. Fields Jr., in charge of land forces during the exercise.

Brim Frost '87 - slightly smaller with 24,000 troops - focused primarily on unconventional warfare, where Alaska forces faced guerrilla units and defended airfields, remote radar stations, ports, a trans-Alaska oil pipeline pump station and other sites from attack.

Planners said they will emphasize safety throughout Brim Frost '89. No live ammunition is to be used, but troops will face temperatures that are expected to plummet to 50 degrees below zero.

''Safety is a very challenging thing,'' McInerney said. ''If you don't have any accidents, then it's a tribute to your professionalism.''

''Our track record in the past has been very good,'' Fields said. ''Last month, 3,500 soldiers at Fort Greely trained in weather that was 44 below zero and they came through the exercise with no serious cold-related injuries.''

Fields said at a news conference Wednesday there is a lot of difference between simply being out in the cold and operating in the cold.

''We'll not back off our exercises simply because the weather drops,'' Fields said. ''It teaches you how to cope. Our potential adversaries are very good at this business.''