Caeleb Dressel celebrates victory in the men's 50m freestyle at the Tokyo Olympics

Tokyo (AFP) - Caeleb Dressel powered to his fifth swimming gold medal of the Tokyo Olympics on Sunday as the United States won their duel in the pool with Australia ahead of the hotly anticipated men’s 100 metres showdown on the track.

Elsewhere on day nine in Japan, Xander Schauffele is well-placed to win gold in the golf tournament while Germany’s Alexander Zverev takes on Russia’s Karen Khachanov in the men’s tennis final.

US gymnastics great Simone Biles, struggling with a debilitating mental block, withdrew from the floor final, leaving her with just one more chance of competing in Tokyo.

Dressel dominated the men’s 50m freestyle final, setting a new Olympic record of 21.07sec and then returned to help his team smash the world mark in the men’s 4x100m medley relay.

The American also won the 100m freestyle, 100m butterfly and the 4x100m freestyle relay earlier in the Games.

The other undoubted star of the pool in Tokyo was Emma McKeon, who grabbed her fourth gold to become the first woman to win seven swimming medals at a single Games when she helped Australia to the women’s 4x100m medley relay crown, less than 40 minutes after winning the 50m freestyle.

US swimmer Robert Finke touched first in the men’s 1500m freestyle to make it a distance double after winning the 800m earlier in the meeting.

The United States ended with 11 golds in the pool, two ahead of fierce rivals Australia, whose nine golds marked their best-ever showing.

Australia's Emma McKeon won seven medals at the Tokyo Olympics

Dressel, 24, failed to get close to matching Michael Phelps’ eight-gold haul in at the 2008 Beijing Games but he leaves Tokyo with his position unchallenged as the biggest name in swimming.

The American, who also won two relay golds at the Rio 2016 Games, set Olympic records in both the 50m and 100m freestyle and smashed his own world record in the 100m butterfly.

“I’m proud of myself,” he said. “I think I reached what my potential was here at these Games.

“It was just really fun racing. I’ll give myself a pat on the back and then I’ll just put it away and move forward. I’m going to take a break here – I’m pretty over swimming. “

McKeon, 27, is just the second woman to win seven medals at one Olympics in any sport, after Ukrainian gymnast Maria Gorokhovskaya in 1952, and is now Australia’s most successful Olympian with five gold medals and 11 overall.

“I look at the athletes that have gone before me and have been so impressed and inspired by what they’ve done but I’ve never been into the stats and medal counts,” she said.

“But to be in that kind of company, it’s an honour and I know I’ve worked hard for it.”

- Bolt crown up for grabs -

Later on Sunday, Usain Bolt’s Olympic 100m crown is up for grabs on the second day of action in the cavernous, spectator-free Olympic Stadium.

China's Gong Lijiao celebrates after winning the women's shot put at the Tokyo Olympics

The pandemic-postponed 2020 Games are the first since Athens 2004 to be held without Jamaican sprint king Bolt, who retired in 2017 after winning the 100m-200m sprint double in Beijing, London and Rio.

The race looks wide open if the first round is anything to go by. Trayvon Bromell, the American who owns the fastest time this year of 9.77sec, only scraped through as a fastest loser after finishing fourth in his heat.

In the morning session, China’s Gong Lijiao lived up to her pre-Olympic form by winning gold in the women’s shot put, denying New Zealand veteran Valerie Adams a third successive gold.

Xander Schauffele in action during the fourth round of the Olympics golf competition

Gong managed a personal best of 20.58 metres on her sixth and final attempt, having led the competition from her opening effort of 19.95m.

An emotional Gong, 32, told Chinese TV: “I’ve achieved it, I’ve finally done it. The last five years, they were really hard. I’m getting older and getting injured more.”

The golf competition is set for a thrilling climax at the Kasumigaseki Country Club, with a clutch of players including Slovakia’s Rory Sabbatini and Britain’s Paul Casey chasing down US star Schauffele.

With Biles taking a back seat due to mental health issues, freshly crowned all-around champion Sunisa Lee goes for uneven bars gold as the apparatus finals begin.

Biles’s withdrawal from the floor final leaves her just Tuesday’s beam as she wrestles with the “twisties”, a mental condition which leave gymnasts unable to orientate themselves in mid-air.

“Simone has withdrawn from the event final for floor and will make a decision on beam later this week. Either way, we’re all behind you, Simone,” USAG tweeted.