Melbourne –

Ariarne Titmus may bow out of her swimming career at next year's Paris Olympics if unable to find motivation to continue, the Australian champion said.

Titmus, the Olympic 200 and 400-meter freestyle champion, said she had spoken to her coach Dean Boxall about her future and did not want to think beyond the next 12 months.

"I don’t know what I’m going to do after Paris," Titmus told reporters. "I plan to continue, but you never know.

"It’s certainly not a love thing or a body thing. I think if I went to Paris and won again, certainly (there might be) a motivational factor. ... It becomes harder to keep training at the same level when you have essentially achieved everything you wanted to achieve."

Titmus, whose rivalry with American great Katie Ledecky lit up the Tokyo Games, qualified for Australia's team for next month's world championships in Fukuoka by winning the 400 freestyle at trials in Melbourne on Tuesday.

Her time of 3 minutes and 58.47 seconds was an improvement on her modest 4:00.49 set at national championships in April, but it was still well adrift of the world record set by Canadian teen sensation Summer McIntosh.

McIntosh, 16, smashed Titmus' previous world record with a swim of 3:56.08 at the Canadian trials in March.

Titmus, Ledecky and McIntosh are set to battle for the 400 freestyle title at Fukuoka.

The three swimmers all have strong claims.

Titmus won the event at the 2019 world championships in Gwangju but skipped last year's in Budapest, which Ledecky won ahead of runner-up McIntosh.

Titmus said the three swimmers were "quite even" going in to Fukuoka but McIntosh was relatively short of big-event experience.

"I feel like Summer hasn't really had that experience yet, racing on the international stage with the big pressure, so it'll be interesting to see how she goes," said Titmus.

"But props to her if she goes in as the favorite."