LOS ANGELES, June 19, 2024 (BSS/AFP) - Regan Smith clocked a world record 57.13sec to win the 100m backstroke at the US Olympic trials in Indianapolis, Indiana, on Tuesday, throwing down a challenge to Aussie Kaylee McKeown six weeks before the Paris Games.

Smith eclipsed the world record of 57.33 set by McKeown in Budapest in October 2023.

"It was part of the plan," Smith said of regaining the record she held back in 2019.

She'd signalled her intentions by lowering her American record to 57.47 in the semi-finals and with Katharine Berkoff pushing her all the way at Lucas Oil Stadium she came up with a late push to slice two-tenths of a second off McKeown's mark.

"I'm so proud of myself," said Smith, who earned two silvers and a bronze at the Tokyo Olympics. "Backstroke is hard for me sometimes, but to fight back like this and get that back means a lot."

Berkoff finished second in 57.91 to set up a powerful US one-two punch in the event in Paris, where McKeown will still be a formidable rival. She posted the 57.41sec at the Australian trials last week.

In his first event of the trials, Tokyo Games star Caeleb Dressel made it safely into the men's 100m freestyle final with the third-fastest time of the semis.

Dressel's five gold medals in Tokyo included the 50m and 100m free and the 100m butterfly.

But he arrived at the trials with his level something of a mystery after he stepped away from the sport abruptly at the 2022 world championships. After a nine-month break he failed to qualify for the 2023 worlds.

Chris Guiliano, already Paris-bound after finishing second to Luke Hobson in the 200m free, topped the semi-finals in 47.25sec.

In the second semi, 21-year-old Jack Alexy held off Dressel, Alexy winning in 47.33 and Dressel touching in 47.53.

It was Dressel's fastest and two years, and he was beaming as he checked the scoreboard and shook hands with Alexy over the lane rope.