President Bush will make a huge detour en route to Canada on Tuesday to visit firefighters in Arizona battling a ferocious blaze that has burned more than 500 square miles.

Bush planned to survey by aircraft the damage from two fires that converged over the weekend. The fires in the eastern part of the state have destroyed at least 329 houses and 16 businesses and forced 30,000 to flee their homes.

On the ground, he is to receive a situation briefing from emergency and rescue teams, then meet with off-duty firefighters and evacuated families who have sought shelter at the domed indoor football stadium of Round Valley High School in Eagar, Ariz.

White House aides scrambled late Monday to arrange the last-minute trip, Bush's first as president to the site of a natural disaster.

From Arizona, Bush heads to the Group of Eight summit in Kananaskis, Alberta, through Thursday.