DOHA: United States swimmer David Johnston swam a personal best to top qualifying for the 400 metres medley final at the World Championships on Sunday, while Canada's Tessa Cieplucha took top seed for the women's 400m.
With France's world champion Leon Marchand skipping Doha, Texas University student Johnston won his heat in four minutes and 12.51 seconds to upstage U.S. team mate and defending silver medallist Carson Foster, who qualified fourth.
Britain's former European champion Max Litchfield was second fastest in the heats, only 0.03 seconds slower than Johnston, while Japan's Olympic bronze medallist Daiya Seto was third.
The women's 400m medley is wide open, with none of the medallists from last July's World Championships in Fukuoka competing.
Former short course world champion Cieplucha swam 4:40.80 to top the timesheets ahead of Serbia's Anja Crevar.
The United States are top seed for the men's medley relay final later on Sunday, ahead of the Netherlands and third seed Spain.
Canada took top seed for the women's medley relay ahead of Sweden and Australia.
Eight gold medals will be awarded in the final evening session later on Sunday, headlined by Sarah Sjostrom's 50m freestyle title defence.
The men's 1,500m freestyle gold will also be up for grabs, along with non-Olympic titles for the men's 50m backstroke and the women's 50m breaststroke.