Ian Thorpe led the Australian assault yesterday as the hosts pulverised their own men's 4 x 200 freestyle relay world record at the Pan Pacific swimming championships in Sydney.

The 16-year-old, who had already set three world marks at the championships, only narrowly missed his own record as he spurred the Australian quartet to a time of seven minutes 08.79 seconds - over three seconds under the mark set by the Australian team at last year's Commonwealth Games.

Team-mates William Kirby, Grant Hackett and Michael Klim followed up in style, gradually leaving the US quartet behind as if to proclaim Australia's ownership of the Sydney Olympic pool.

"We were team athletes tonight. We got the result as a team and we shared the emotions tonight," Thorpe said.

"It's totally different to winning an individual gold."

It took to seven the number of world records set in the first four days of the championships.

In other races, American Tom Malchow set a record pace for the first three laps of the men's 200 metres butterfly final but ran out of puff in the final leg. Malchow took the gold medal in a time of 1:55.41, just 0.19 seconds outside the elusive 1:55.22 set by Russia's Denis Pankratov in 1995.

Australian veteran Susan O'Neill cruised to gold in the women's 200 freestyle with a Commonwealth record of 1:58.17 and then set a personal best of 2:06.53 in the semi-finals of her favourite event, the women's 200 butterfly.

That time put her only 0.57 seconds from the oldest record in swimming, set by American Mary T Meagher in 1981. Meagher herself has said she will be keeping her fingers crossed for O'Neill when she makes a tilt at the record in Thursday's final.

Canadian crowd favourite Joanne Malar took the gold medal in the women's 200 metres individual medley in a personal best time of 2:13.63 after catching fast-starting Japanese Tomoko Hagiwara. Hagiwara settled for silver in 2:14.31. Malar also won the 400 metres individual medley on Sunday.

But the champions were relegated to bit players by the heroics of Thorpe and the ultra-talented Australian men. Thorpe's lead-off time in the 200 freestyle relay was 1:46.28, a time second only to his own record of 1:46.00 set on Tuesday.

Thorpe had earlier suffered his first setback of the championships when he was edged out of the 100 freestyle final by team-mates Klim and Chris Fydler, despite finishing fourth fastest of the 16 semi-finalists. Pan Pacific rules allow only two swimmers from each nation to make the finals.