KAZAN, Russia (AP) Australia's Campbell sisters signaled they will be tough to beat in the 100-meter freestyle after claiming two of the top three times in the preliminaries at the swimming world championships on Thursday.
Cate Campbell and Sweden's Sarah Sjostrom posted the fastest time in separate heats, each touching the wall in 53.22 seconds.
''I executed a good race plan. I could see where everyone was,'' Cate Campbell said. ''It was nice and easy, nice and relaxed.''
Swimming one lane over from her sister, younger sibling Bronte Campbell was third in 53.50 and Olympic champion Ranomi Kromowidjojo of the Netherlands qualified fourth.
The sisters joined hands after their heat as they looked up at their times.
Cate Campbell is the defending champion, having won two years ago in Barcelona in 52.34. That experience should help in the semifinals later Thursday, and in the final Friday.
''Relax, be smart about racing, don't stress, don't tighten up. All of things that sound really easy to do but it's actually the hardest,'' Cate Campbell said. ''The best swimmers are the ones that almost don't try the most. ... It's just about relaxing and enjoying it.''
Femke Heemskerk, another Dutch contender, advanced fifth, while Americans Simone Manuel and Missy Franklin made the semifinals in seventh and 10th, respectively.
Katinka Hosszu, the ''Iron Lady'' from Hungary, did not start.
Another Australian, Cameron McEvoy, was the leading qualifier for the men's 100 free final later.
On a strong morning for Australia, Mitchell Larkin led the 200 backstroke heats in 1:55.88, nearly a full second ahead of second-placed qualifier Ryosuke Irie of Japan, who touched in 1:56.68.
Larkin already took gold in the 100 back.
''I think it's quite achievable to win both,'' Larkin said. ''It's a process, but I'd like to stand up there again. I came here to win.
''They're different swims. The 200 is more about being paced correctly and not going out really fast in the first heat like I did at trials,'' Larkin added. ''But I think I've got big improvements especially in the 200.''
Americans Ryan Murphy and Tyler Clary, the Olympic champion, where third and sixth, respectively.
Ryan Lochte decided not to defend his title in this event, although the American standout was the overwhelming favorite for gold in the 200 individual medley final later.
There was a surprise when defending champion Yulia Efimova failed to advance from the 200 breaststroke heats in 17th place, one spot below the cutoff.
Efimova returned in March from a 16-month doping ban after testing positive for the banned steroid DHEA.
The Russian won gold in the 100 breast two days ago.
Kanako Watanabe of Japan led the 200 breast heats in 2:23.29 ahead of Micah Lawrence of the U.S. and Hrafnhildur Luthersdottir of Iceland.
Germany's Marco Koch led the men's 200 breast in 2:09.12, while three-time defending champion and Olympic gold medalist Daniel Gyurta was fifth.
Adam Peaty of Britain, who swept the 50 and 100 breast titles and helped Britain to gold in the mixed medley relay, failed to advance in 26th
''These last few days have taken so much out of me, emotionally and physically,'' Peaty said. ''Winning medals takes a lot out of you.''
With Federica Pellegrini handling the anchor leg, Italy led the 4x200 free relay. The U.S. was 0.10 behind and Australia was third, 0.15 back.
With Katie Ledecky and Missy Franklin swimming the final later, the U.S. will be the favorite.
Tilka Paljk from Zambia hyperventilated after placing 46th in the women's 200 breast and was carried out of an interview area on a stretcher.
Andrew Dampf can be followed at www.twitter.com/asdampf