Michael Phelps and Katie Hoff got the US Olympic trials off to a spectacular start with world records in the 400 metres individual medleys on Sunday.

Officials had promised fireworks during the eight-day competition and the first night produced two world records in three finals.

Phelps, targeting Mark Spitz's record of seven gold medals at a single Games in Beijing [Images], stormed to the wall ahead of good friend Ryan Lochte in a time of four minutes 5.25 seconds, slicing almost a second of his old mark.

"I left everything in the pool," Phelps, who swam in the controversial hi-tech Speedo LZR Racer swimsuit, told reporters. "I would never have been able to do it without Lochte beside me. He is a great friend and a great competitor.

"I definitely started the meet off on the right foot.

"When I heard the crowd I had the feeling something special could happen."

With the arena still buzzing from Phelps's performance, Hoff brought the near capacity crowd of 12,000 to its feet again by powering to the wall in 4:31.12 to reclaim the world record she surrendered to Australia's Stephanie Rice in March.

"It was definitely special for me," said Hoff, who at 15 was the youngest member of the U.S. Olympic team in Athens.

"I was trying to keep that off my mind a little bit because with IMs I kind of pushed and pushed and hyper-focused on them and it really didn't happen for me until I just stopped thinking about it.

"Watching the first race of the meet was definitely inspiring, it gave me chills and got me psyched up for my race."

DRAMA-FILLED

The men's 400m freestyle failed to produce a world record but was full of drama with Larsen Jensen winning in a time of 3:43.53 ahead of Peter Vanderkaay and Erik Vendt. The three swimmers were separated by just 0.39 seconds.

Brendan Hansen almost added another world record, posting the top qualifying effort of 59.24 in the 100m breaststroke semi-finals. The time was the fastest this year and just off Hansen's own world record of 59.13.

Phelps, six-times Olympic gold medallist, had been scheduled to swim nine events over the eight days but withdrew from the 400m freestyle before the preliminaries on Sunday.

He is expected to swim only the 200m freestyle on Monday after his name did not appear on the start list for the 100m backstroke preliminaries.

"Being able to start the meet the way I did helps me relax a little bit more," said Phelps, who will celebrate his 23rd birthday on Tuesday.

"I didn't want to lose that race, I was pretty fired upcoming into the final. I just went out there and did whatever I could to get my hand on the wall first.

"You saw how emotional and excited I was after the race. I never really take one hand and thrash the water, I was pretty fired up."