Australia's Ian Thorpe smiles after competing in the men's 200m Freestyle heats at the 2012 Australian Swimming Championships to qualify for the 2012 London Olympics, in Adelaide, March 16, 2012. [Photo/Agencies]

ADELAIDE - Five-times Olympic champion Ian Thorpe's bid to compete at the London Games remains alive after he eased into the semi-finals of the 200 meters freestyle at Australia's national swimming trials in Adelaide.

Thorpe, who will also compete in the 100 freestyle at the weekend, finished tied for second in his heat to be equal fifth fastest of the top 16 swimmers who will contest the semi-finals in the evening session at the South Australia Aquatic and Leisure Centre.

The headline act at Australia's trials, Thorpe mounted the starting block to a huge roar from stands packed with noisy schoolchildren and pushed out to a strong lead by the halfway turn before being reeled in by pace-setter Ryan Napoleon.

Thorpe posted a time of one minute, 49.16 seconds to finish in a dead heat with David McKeon, his fastest swim in the distance since returning to competition in November, but more than five seconds adrift of his personal best set in 2001.

"It's a pretty decent time. I'm happy with that swim this morning," the 29-year-old said in a brief poolside interview before heading off to prepare for the semi-finals.

Should Thorpe make the final but miss out on a berth for the individual event reserved for the winner and runner-up, a top-six finish will at least ensure he is considered for selection to the four-member freestyle relay team.

After more than five years away from the pool, the 11-times world champion announced his return to the pool just over a year ago with the aim of qualifying for his third Olympics.

Australia's Ian Thorpe swims during the men's 200m Freestyle heats at the 2012 Australian Swimming Championships to qualify for the 2012 London Olympics, in Adelaide, March 16, 2012. [Photo/Agencies]

He has struggled to post competitive times since returning to the pool, fuelling rampant speculation by local media that he is keeping his powder dry, despite repeatedly writing off his own chances.

Thorpe's best chance making the Australia team is in the 200 freestyle, with the 100 boasting an ultra-competitive field including world champion James Magnussen and the other three members of the gold-medal winning relay team from last year's world championships in Shanghai.