Washington - Natalie Coughlin set another world record in the women's 100-metre backstroke Tuesday, her second time in as many days at the US Olympic Swimming Trials in Omaha, Nebraska. 

Coughlin swam in 58.97 seconds on Tuesday, to clinch the final and securing a spot on the US team for the Beijing Games. On Monday her record of 59.21 was broken by Hayley McGregory in a preliminary heat. However, just two minutes later, Coughlin regained the record in her heat with a time of 59.03. 

In Tuesday's final Margaret Hoelzer came in second with McGregory finishing third in 59.42. 

Aaron Peirsol bettered his world mark in the men's 100-metre backstroke in a time of 52.89. He bettered by .09 second the time he set at last year's world championships in Melbourne. Matt Grevers finished second in 53.19, followed by Ryan Lochte in 53.37. 

Michael Phelps secured two more Olympic berths by posting the third fastest time ever in the 200m freestyle in 1:44.10 and the top qualifying time of 1:54.02 in the 200m butterfly. 

Jessica Hardy is going to her first Olympics with a win in the 100m breaststroke in 1:06.87, beating 2000 Sydney gold medalist Megan Jendrick. 

Six world records have been set in the first three days of the US trials. (dpa)