Australian Libby Lenton swam the first leg of a mixed relay in a world-record time for the 100-meter freestyle Tuesday at the Duel in the Pool meet featuring the best swimmers from the United States and Australia.
Lenton, swimming against Michael Phelps in the opening leg of the 400-meter relay, finished in 52.99 seconds to break German Britta Steffen's mark of 53.30 by nearly a third of a second.
Steffen set her mark last August at the European championships in Budapest.
Lenton won five gold medals for Australia at the world championships which ended Sunday in Melbourne, while Phelps picked up seven golds.
There was initial speculation that Lenton's swim would not count because of the unusual nature of her racing against Phelps and that he could be seen to be pacing the Australian.
But Swimming Australia chief executive Glenn Tasker said the swim would stand as a world record.
"It was a fair race, and FINA said it will count," said Tasker.
Lenton said she had some pre-race banter with Phelps.
"I was trash talking ... asking what he has got and telling him if he is going to bring it tonight," Lenton joked. "I think deep down he was really scared of me.
"Before the race he said good luck. He is a good competitor to race against and I will remember that for the rest of my life, that I raced against Michael Phelps."
Phelps swam a respectable 48.72 seconds over his 100 meters.
The Americans beat Australia 181.5 to 129.5 in points in the event at the 2000 Sydney Olympic pool.
It was the third straight time the U.S. team has won the head-to-head match-race competition. The previous two events were held in the United States.