BEIJING — LaShawn Merritt has upset defending champion Jeremy Wariner to lead a U.S. sweep of the medals in the 400 meters at the Olympics.

Merritt pulled away down the stretch Thursday night to win in 43.75 seconds — nearly a full second ahead of silver medalist Wariner, who finished in 44.74.

The third American in the final, David Neville, did a head-first dive across the finish line and wound up with the bronze in 44.80.