A U.S. B-52 bomber flying over northern Canada Thursday began the first test of an advanced "stealth" cruise missile outside the United States, military officials said Thursday.

Maj. Jan Martinsen, spokeswoman for Canadian Forces in Cold Lake, Alberta, said the bomber with the cruise missile strapped to it began the four-hour test about 7:15 a.m. MST.The bomber left Edwards Air Force Base, Calif., late Wednesday.

A test scheduled for Wednesday morning was canceled because of a severe blizzard that was causing icing, turbulence and heavy snow in the northern parts of the route.

Throughout its four-hour journey, the missile was to remain attached to the B-52.

The bomber was to fly over the Beaufort Sea, follow the McKenzie River valley, then turn eastward near the junction of the borders of the Northwest Territories, Alberta and British Columbia. The plane then was to continue southward to the Primrose Lake air weapons range in northern Alberta before returning to the United States.

Defense experts in Canada and the United States said in interviews that successful tests over northern Canada were essential to the cruise missile's eventual production.

Canada began testing cruise missile weapons in February 1985 under an agreement allowing six flights each winter.