Michael Phelps and his US swim team have vowed to reassert their dominance over Australia at this week's Pan Pacific Championships in southern California.
The winner of a record eight gold medals at the 2008 Olympics in Beijing, has made a last minute change to his PanPacs program.
He's dropped the 200 metres freestyle, but added the gruelling 400 individual medley which he hasn't contested since setting a world record in Beijing.
Phelps, who's 25, will also swim the 200 individiual medley and the 100 and 200 butterfly and relays.
He says he's not in the best physical shape, but feels he has a good shot at winning a place in the American team for the next world championships in the 400 individiual medley