Shanghai: Michael Phelps' rocky season took another turn for the worse Tuesday when the 14-time Olympic gold medallist was stunned in the world championships 200m freestyle by US team-mate Ryan Lochte. (Agencies)
Phelps led over the first 100m until Lochte surged from third place to claim a narrow win in 1min 44.44sec, with defending champion Paul Biedermann of Germany third.
The result means Phelps, the Olympic champion and former world record-holder in the event, fails to regain the crown he lost to supersuit-wearing Biedermann two years ago. South Korea's Park Tae-Hwan was fourth.
"Michael and I have been battling head-to-head for almost eight years now," said Lochte. "It's been going back and forth and it's definitely been a good rivalry.
"He's a great competitor. He's one of the world's great swimmers. I'm just privileged to swim on the same team, even the same event."
Phelps remains on course for a possible five gold medals in Shanghai, which would match his haul in Rome two years ago. He claimed bronze on Sunday when the United States suffered a rare defeat in the 4x100m freestyle relay.
Meanwhile Camille Lacourt and Jeremy Stravius bizarrely became France's first male world champions -- in the same race. Both swimmers finished the 100m backstroke in 52.76, only the second dead heat in world championships history.
The unusual result echoes 2007's 100m freestyle world title race when Italy's Filippo Magnini and Brent Hayden of Canada both topped the podium with identical times of 48.43.
In other results, America's Rebecca Soni defended her 100m breaststroke world title ahead of Olympic champion Leisel Jones of Australia and Asian title-holder Ji Liping of China.
And Zhao Jing secured China's second swimming gold in another upset win when she beat Olympic title-holder Natalie Coughlin into third place in the women's 100m backstroke.
Zhao finished in 59.05sec, just one-hundredth of a second faster than 2009 silver-medallist Anastasia Zueva of Russia.
"The really difficult thing about backstroke is you never really know where you are in the race. In prelims on Monday morning I thought I was in fourth place and I was ahead," Coughlin said.
"Being that the meet's here in Shanghai I knew the Chinese were going to be very, very strong."
The win for Zhao, 20, follows 15-year-old Ye Shiwen's stunning triumph for China in the women's 200m individual medley, when she shocked the reigning world and Olympic champions on Monday.
Also on Tuesday, Danish 800m world champion Lotte Friis built an early lead and stayed ahead to win the women's 1500m by six seconds from American world record-holder Kate Ziegler and China's Li Xuanxu.
Phelps has said he is into the final year of his career as he builds towards London 2012, where he will aim to add to his 14 Olympic titles -- including a record-breaking eight in Beijing.
The 26-year-old Baltimore Bullet admits he has struggled for motivation since the 208 Games, and has slumped to a series of shock defeats this season. But he says he is back on track and training well under coach Bob Bowman.
Phelps arrived in Shanghai with 22 world titles but suffered a disappointing start when the United States finished third in the 4x100m relay, ending an unbeaten world and Olympic streak stretching back to Athens 2004.
In 2009, Biedermann beat Phelps by a wide margin in the 200m freestyle and shattered his world record with a time of 1:42.00. The German was wearing one of the high-tech, polyurethane suits that are now banned.
Phelps also finished second in his men's 200m butterfly semi on Tuesday to secure a place in Wednesday's final.
Shanghai: Michael Phelps' rocky season took another turn for the worse Tuesday when the 14-time Olympic gold medallist was stunned in the world championships 200m freestyle by US team-mate Ryan Lochte.