Defending champions Australia were disqualified after their heat in the men's 4x100 medley relay at the World swimming championships on Sunday.

Officials ruled that there had been a faulty takeover between backstroker Josh Watson and breaststroker Jim Piper at the end of the first leg.

Australia finished first in their heat in a time of three minutes 37.29 seconds after world 200 and 400 freestyle champion Ian Thorpe had swum a strong freestyle length to overhaul France's Frederick Bousquet.

The time would have qualified them as third fastest for the final later on Sunday.

The United States were the fastest qualifiers in a championship record of 3:34.80, with Japan second in 3:37.08. France were third fastest in 3:37.57.

Russia, without 50 and 100 freestyle champion Alexander Popov, finished fourth in 3:38.14. opov is expected to race in the final.

World record holder Michael Phelps of the United States qualified second fastest for the men's 400 metres individual medley.

Phelps, the 200 medley and 200 butterfly champion, touched in 4:15.72, well outside his record of 4:10.73, to win the final heat.

Laslzo Cseh of Hungary was the fastest qualifier in 4:14.11 with Japan's Takahiro Mori third fastest in 4:17.12.

Olympic and defending champion Yana Klochkova of the Ukraine was the third fastest qualifier in the women's 400 individual medley in 4:44.14, well outside her world record time of 4:33.59.

Hungary's Eva Ristov, the silver medallist in the 400 freestyle and 200 butterfly, was the fastest qualifier in 4:42.89.

Risztov, 17, finished second behind Klochkova in both individual medley events at last year's European championships.

Nicole Hetzer of Germany was second fastest in 4:43.48, while 2001 bronze medallist Beatrice Caslaru of Romania was fourth in 4:44.26.

The championships finish later on Sunday with seven finals, including the men's 1500 freestyle, both individual medley events and the men's 4x100 medley relay.