With the great Michael Johnson absent, Moncur stepped forward to fill the American's shoes and take gold in 44.64 seconds.

But Moncur, who did not reach in the Olympic final last year, had to dig deep to hold off German Ingo Schultz, who recorded 44.87, and Jamaica's Gregory Haughton (44.98).

Olympic champion Johnson decided not to compete in Edmonton and is concentrating this season on grand prix meetings.

US college champion Moncur made up for his disappointment at the Sydney Games where he failed to make the final by one-hundredth of a second.

He said: "I used that for my major motivation coming in to this race.

"I had a picture of the finish on my wall and just went out there and practiced hard.

"Coming here made my dream, which was becoming world champion, a reality."

Johnson tribute

Moncur paid tribute to Johnson, who broke the world 200m record at the 1996 Atlanta Olympics and the 400 mark at the 1999 Seville World Championships.

"I don't think anyone can do what he has done in the 400m, being consistent over the years," Moncur said.

"To come halfway to what he has done would be a major accomplishment.

"I'd like to think that I'm on a roll and I'm looking forward to future world championships."

Schultz said his aim had been to qualify for the semi-finals.

"I'm still dreaming, I'm waiting for the wake-up," he said.