Paris 2024: Katie Ledecky sets up 400m showdown with champion Ariarne Titmus

The American great qualified fastest for the final as the Paris swimming event launched in a febrile atmosphere on Saturday.

Three years after Titmus took Ledecky's Olympic crown in a Tokyo thriller, the pair lined up next to each other on the blocks and were again neck-and-neck at a rocking La Defense Arena before Ledecky pulled away in the final lap.

Ledecky finished first in four minutes 2.19 seconds, nearly three-tenths of a second quicker than second-ranked Titmus.

Canadian wunderkind Summer McIntosh is also in the mix for what should be an enthralling 400 decider later on Saturday, having qualified fourth behind New Zealand's Erika Fairweather.

"It's good to walk out to a full stadium for a prelims race," seven-time Olympic champion Ledecky told reporters.

"It felt very similar to our Olympic trials a few weeks back, so I'm excited to see the finals atmosphere tonight as well and I'm happy to get a good first one on the board."

Titmus, the world record holder, expressed contentment with her performance in the heats, stating that she was focused on conserving energy.

She dismissed the notion that Ledecky's top ranking in the final would give her a psychological advantage.

China's Zhang Yufei led the 100 meters butterfly heats, followed by Japan's Mizuki Hirai and American Torri Huske. Gretchen Walsh and Maggie MacNeil also advanced to the semi-finals.

Zhang, who was previously implicated in doping allegations, expressed concerns about being judged by her peers due to the controversy.

The World Anti-Doping Agency attributed the positive test results to contamination from the team's hotel kitchen.

Adam Peaty, the world record holder, expressed his confidence after qualifying second fastest for the semi-finals in the 100 breaststroke event. He mentioned that his experience has helped him remain calm and composed.

Meanwhile, the Chinese swimmer Qin Haiyang had a slow start, qualifying ninth in the heats. In the men's 400 freestyle final,

Germany's Lukas Maertens secured the top rank, with Australia's former world champions Elijah Winnington and Sam Short also expected to contend for the gold. In the women's 4x100m freestyle relay final,

Australia is the top seed, while China leads the men's 4x100m freestyle final. The United States finished fourth quickest in the men's 4x100m freestyle heats.