Phelps sinks medley world record

America's Michael Phelps took the first step towards his quest to equal or surpass Mark Spitz's seven Olympic gold medal haul with a new 400 metre individual medley world record.

The 19-year-old triple world record-holder clocked 4:08.41 on the first day of the U.S. Olympic trials on Wednesday to lower the 4:09.09 standard he set at last year's World Championships in Barcelona.

After trailing his world record pace by 0.2 seconds through the first 100 metres of butterfly, Phelps moved ahead of the former record pace and kept increasing his margin.

Phelps's splits for the four disciplines were: 55.66 seconds for the butterfly, 1:02.19 for the backstroke, 1:12.90 for the breaststroke and 57.66 for the freestyle leg.

The record-breaking performance was not the only outstanding swim of the evening as Phelps's 15-year-old North Baltimore team mate Katie Hoff set a U.S. Open record in winning the women's 400 metre individual medley in 4:37.67.

Her time was also the fastest in the world this year.

Klete Keller, a 2000 Olympic bronze medallist in the 400 metres freestyle, won his event in 3:44.19, breaking Phelps's American record by over two seconds.

Only Australia's Grant Hackett has gone faster this year.