SYDNEY (Reuters) -- Libby Lenton set a women's 100 meters freestyle world record during the Australian national championships at the Melbourne Aquatic Center on Tuesday.

Lenton, 20, won her semifinal in 53.42 seconds, wiping 0.10 seconds off the previous world record set by compatriot Jodie Henry at the 2004 Athens Olympics.

"I felt good and I thought I would just go for it," Lenton said in a televised interview. "I was planning just to do my personal best time, but I am really excited to get the world record."

Henry won Tuesday's first semifinal in 54.52 and was being interviewed on Australian television when her world record fell. "World records can be broken any day," Henry said. "Who is to say I'm not going to go out and break it again?"

Lenton first broke the world record in the semifinals of the Australian trials for the 2004 Athens Olympics, beating the old mark set by Inge de Bruijn.

But she finished second in the final behind Henry then failed to make the final in Athens. Henry broke the world record in the semifinals in Athens before going on to win gold.

Lenton had to be satisfied with an Olympic relay gold medal but has been in great form since. Peak form

She won the 50m freestyle at last year's world championships in Montreal and broke the 100m (twice) and 200m short-course world records last year.

Lenton's record was the second to tumble in as many days at the championships, which double as the Australian trials for the Commonwealth Games.

Jade Edmistone lowered her 50m breaststroke world record to 30.31 in Monday's heats.

Lenton's performance also overshadowed the return of Ian Thorpe, who was competing in his first major competition since Athens.

Thorpe cruised to victory in the men's 200m freestyle final in 1:46.42, but was unhappy with his time, which was 2.36 outside his own world record. "I am a bit disappointed with it, but it served its purpose," Thorpe said.

"There is no reason I felt pretty ordinary and did not swim well today."