Australian Olympic champion swimmer Ariarne Titmus is unable to commit to a re-match with Katie Ledecky yet, citing the mental fatigue of her rivalry with the American great.

Titmus is skipping the world championships in Budapest this month and could also miss the "Duel in the Pool" meet in Sydney in August, where Australian and American swimmers face off.

Titmus is instead preparing for the Commonwealth Games in Birmingham and may take a holiday after that to recharge, which would deny swimming fans a potential showdown with Ledecky.

"Still deciding on Duel in the Pool," she told reporters on Wednesday.

"I know people are looking to see if I'll be racing Katie, it's always a very highly anticipated battle.

"But the battle with her comes with external pressure.

"Last year was huge for me, mentally too, a lot of pressure around my races.

"I didn't really want to have to deal with that pressure again (at Budapest)."

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Titmus set the 400 metres freestyle world record of three minutes 56.40 seconds at the national championships in Adelaide last week, shaving 0.06 seconds off Ledecky's mark from the Rio Olympics.

The 21-year-old last year edged Ledecky by less than a second for the 400m Olympic gold medal at Tokyo but the American turned the tables on the Australian to win the 800m.

While the Ledecky rivalry is on ice for the time being, Titmus is eyeing 15-year-old Canadian Summer McIntosh as an emerging threat at Birmingham and in the leadup to the 2024 Paris Olympics.

McIntosh is the third quickest swimmer in the 400m freestyle this year (4:01.59), behind Titmus and Ledecky.

"I remember when I was Summer's age, I wasn't swimming 4:01, 4:02," said Titmus.

"And she doesn't have the strength yet that we have and when she does she is going to be a force to be reckoned with.

"There is this unbelievable depth ... In Paris the race won't just be between Katie and I."