Soni upsets Jones in 200m breaststroke

American Rebecca Soni has caused a sensational upset in the women's 200 metres breaststroke, defeating Australia's Leisel Jones at the Beijing Olympics.

Jones was the raging favourite going into the race but the 21-year-old Soni streaked clear in the final 50 metres to claim gold and break Jones's world record in a time of 2.20.22.

Jones claimed silver in 2.22.05 with Sara Nordenstam of Norway finishing with the bronze in 2.23.02.

After the race a smiling Jones shrugged off the defeat.

"I just gave it absolutely everything .. I don't care, I'm all done," she told Channel Seven.

"I've had the best time and I think that's the most important part. I'm just so happy in my life that I couldn't care less.

"No commiserations. It's the Olympic Games, it's what it's all about. It was a great experience, she was the better swimmer on the day, she really did a great job, and I couldnt be more happy."

Soni, who qualified fastest for the final, battled tirelessly to stay on Jones's shoulder before taking the lead in the last turn by only 0.01 seconds.

She then went on with the job leaving a clearly sluggish Jones in her wake to eclipse the previous world mark by 0.32 seconds.

It is the 22-year-old Australian's second silver in the event after finishing behind American Amanda Beard in Athens.

Jones has been the undisputed queen of women's breaststroke and broke through for her first individual Olympic gold in winning the 100m event on Tuesday.

"I really couldn't breathe that last 50, I was just digging deep and couldn't breathe. It was like at the (2006) Commonwealth Games," Jones said.

"Rebecca is a pretty good competitor, she was always going to go fast, it's good to see people swimming so fast.

"A silver medal is still a silver medal in the Olympics. I gave it everything, I couldn't have given more. It's been a long week and it's hard to get up for that."

Soni's surprise victory over the world champion reversed a run of defeats the American women swimmers had been experiencing against their powerful Australian counterparts.

"It just kind of flowed, it just happened, it felt great. I just kept it strong and powered to the end," Soni said.

"It feels great. The last 15m I had plenty left in me, I saw Leisel behind and just pushed for the wall.

"I didn't know what was going on, I just went for it. I thought I had a chance, but I wasn't over-confident."

Soni, who underwent minor heart surgery in 2006, was the runner-up to Jones in the 100m final, but she was too strong for the Aussie champion over the extra two laps.

Soni said she had been motivated by the sensational gold medal exploits of American team-mate Michael Phelps.