LaShawn Merritt of the US satisfied his hunger for success on Tuesday by regaining the 400m title at the world championships while defending champ Kirani James of Grenada faded badly to finish seventh.

Merritt took the race from the gun and went hard over the first 200. He still had plenty left in the tank coming into the home stretch to seal victory in a world-leading 43.74 seconds.

Compatriot Tony McQuay (44.40) made it a 1-2 for the US, which has now won all but four of the men's world titles in the event.