Peirsol will be tough to beat in Beijing

Aaron Peirsol and Natalie Coughlin set new world records in the men's and women's 100m backstroke at the United States Olympic trials in Omaha.

Peirsol beat his own world record when he touched in at 52.89 seconds.

Coughlin also eclipsed her own world best to become the first woman to go under the 59-second mark in 58.97 sec.

Michael Phelps set a United States open record in the 200m freestyle, finishing in one minute 44.10 seconds - the fastest time in the world this year.

Peirsol's time underlined the challenge that will be faced by British pair Liam Tancock and Gregor Tait in Beijing.

Coughlin initially broke the world record in August 2002 when she became the first woman to break the one-minute barrier.