American 400 metres champion Jeremy Wariner succeeded Michael Johnson as the Olympic gold medallist on Monday with a personal best of 44.00 seconds.

He is now the eighth fastest man in history in the all-time list headed by Johnson's world record 43.18 set at the 1999 Seville world championships.

Wariner, 20, led the fourth United States sweep in an Olympic 400 race, winning ahead of team mates Otis Harris (44.16) and Derrick Brew (44.42).

"We wanted to go one-two-three," Wariner said. "We worked hard, we fought hard and we came out on top.

"It hasn't sunk in yet, it's going to hit me in a couple of days."

Wariner is coached by Clyde Hart, the man who guided Johnson to the 200-400 double at the 1996 Atlanta Olympics and to the 400 gold in Sydney four years later.

"My coach told me everything had gone to plan," he said. "I talked to Michael after the race and he was really excited, he didn't say a lot.

"I won't have time to celebrate, I have to get ready for the 4x400 relay."

Hart said: "After Michael I didn't think I'd have another champion."

Wariner, who won the U.S. title this year in 44.37 seconds, ran a conservative first 200 metres with Harris taking the early lead.

He accelerated in the final straight, edging ahead of Harris, to win a narrow but convincing victory.

"We feel really proud and I hope Americans are as proud of us as we are of the clean sweep," Harris said.

Brew added: "It's great for the U.S. to win three medals in the same event."

Johnson told BBC television that Wariner was more mature than his years would indicate.

"He is actually able to hold his form and hold his composure coming down the home stretch when Otis Harris is right beside him and pressuring him."

"It is the biggest event of his career and he holds his composure to come through for the victory."