Adelaide (Australia) (AFP) - Australia’s Kaylee McKeown threw down the Olympic gauntlet to American rival Regan Smith by smashing her 100m backstroke world record Sunday, while Ariarne Titmus fired a warning shot to superstar Katie Ledecky with the second fastest 400m freestyle ever.

McKeown, 19, touched in 57.45sec at the Australian Olympic trials in Adelaide, sweeping past Smith’s all-time mark of 57.57 set at the 2019 world championships, dedicating it to her father who died last year.

World champion Titmus was also red-hot, narrowly missing American great Ledecky’s 2016 world record of 3:56.46. She was under the pace for much of the race but just missed out, hitting the wall in a sizzling 3:56.90.

Reigning Olympic 100m freestyle champion Kyle Chalmers booked his ticket to Tokyo after winning the 200m, while Mitch Larkin, the 200m backstroke silver medallist at Rio in 2016, made his third Games by claiming the 100m back.

“I just can’t believe it. I just wanted to come in tonight and blow out the cobwebs,” an emotional McKeown said poolside in Adelaide with tears in her eyes.

“It’s been a huge year for me and my family. It’s been 10 months since my dad passed today. So with that behind me and doing that I think he would be very proud.”

McKeown’s father died from brain cancer aged just 53 and she has a tattoo on her foot which says: “I will always be with you.”

McKeown is shaping up to be a serious multiple gold medal contender in Japan.

She is also expected to qualify in the 200m backstroke, having recently set the fourth quickest time in history, and the 200m individual medley, where she owns the world’s best time this season.

Veteran Emily Seebohm, silver medallist at London in 2012, hit the wall second in 58.59 behind McKeown to qualify for her fourth Olympics.

Titmus’s time was the second quickest in history, setting the scene for a showdown with Ledecky, having upset her to claim gold at the 2019 worlds in South Korea.

“I know it’s going to take a world record to win at the Olympics with her in the field,” she said. “It gives me confidence that I went close to that tonight.

“I’m a bit shocked, honestly, I didn’t think I would go that quick,” added the 20-year-old as tears flowed.

She will also swim the 200m and 800m in Adelaide, and is a key member of the Australian 4x200m freestyle relay that holds the world record.

Chalmers, who stunned the swimming world when he won 100m freestyle gold in Rio as an 18-year-old, clocked 1:45.48 to take out the 200m ahead of Elijah Winnington.

Mack Horton was sixth after his failure to qualify for the 400m as defending Olympic champion. He could still make the trip to Japan as a relay swimmer.

Larkin ensured he will be at his third Games by winning the 100m backstroke, but he only just made the grade, equalling the 53.40 time needed.

Swimming Australia has set the bar high at the six-day trials – to qualify, athletes must match or better the time needed to make the final at the 2019 world championships.

Chelsea Hodges (1:05.99) and Jessica Hansen (1:06.69) both managed that in the women’s 100m breaststroke as they set their Tokyo sights on American world record holder Lilly King.

Australia won ten medals in the pool at the 2016 Games in Rio, matching their feat from London four years earlier, but well down on the 20 they clinched in Beijing in 2008.