MELBOURNE - Iga Swiatek booked her second Australian Open semifinal with another spectacular display on Wednesday while Americans reached the last four of the men's and women's singles at Melbourne Park for the first time in 16 years.

Defending champion Jannik Sinner was also at his impressive best as he dismantled local favorite Alex de Minaur 6-3 6-2 6-1 for his 10th victory over the eighth seed in as many matches and returned to the last four at Melbourne Park.

"I felt like today was a great match from my side," said Sinner, who battled illness in the previous round but looked unstoppable on a cool evening at Rod Laver Arena.

"I served very well. Breaking quite early in each set was very important for me and for my game. So, yeah, for sure was the best match of the tournament so far."

Polish world number two Swiatek mowed down eighth seed Emma Navarro 6-1 6-2 at Rod Laver Arena and faces another American in Madison Keys, who overhauled Elina Svitolina 3-6 6-3 6-4.

Ben Shelton wore down Italian Lorenzo Sonego 6-4 7-5 4-6 7-6(4) in a highlight-laden clash and ensured the United States has players in the men's and women's semifinals for the first time since Andy Roddick and Serena Williams in 2009.

Searching for her first Grand Slam title, Keys will be hard-pressed to go further than Swiatek, who has crushed all five of her opponents at this tournament and is the only woman in the semifinals to avoid dropping a set.

A throbbing ball of energy from the first point to the last, the five-times Grand Slam champion broke Navarro to love in the first game and was not prepared to concede a point - even when good sportsmanship might have warranted it.

In the fifth game of the second set and under pressure on serve, Swiatek bolted forward to retrieve a drop that bounced twice before her racket scooped it up.

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Play went on, though, with Swiatek winning both the point and the game with a passing shot, leaving Navarro to remonstrate fruitlessly with the chair umpire.

Having not stopped the rally to dispute the non-call, Navarro had no recourse to challenge it - and Swiatek was not about to give the US Open semifinalist a break.

"I didn't see the replay after this point because ... I wanted to stay focused and didn't want this point to stay in my head for a longer period of time," Swiatek told reporters.

Most eyes have been focused on the top half of the women's draw, where title favorite and double defending champion Aryna Sabalenka booked a semifinal with Paula Badosa on Tuesday.

But it may be the free-swinging Swiatek in pole position for the title, having lost only 14 games in her five matches.

Characteristic aggression

Keys had earlier blasted into a third Australian Open semifinal with characteristic aggression, 10 years after making her first at Melbourne Park.

The 29-year-old from Rock Island, Illinois had lost the last two of her three major meetings with Svitolina, most recently in the fourth round of the 2019 US Open.

She appeared set for another setback as the counter-punching Ukrainian took advantage of Keys' early waywardness on a breezy morning on day 11 of the championships.

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Keys dropped serve in the eighth game with an unforced error and then gifted the set with another mistake, as Frenchman Gael Monfils nodded approval at his wife Svitolina from the stands.

Keys raised her game, though, breaking Svitolina in both the final sets while staying rock-solid on serve.

Shelton, the 21st seed, is the last American in the men's singles draw, having carried on after the third round demise of US Open runner-up Taylor Fritz and the quarterfinal exit of 12th seed Tommy Paul.

Donning a white headband and a technicolour outfit, the 22-year-old brought a matching attitude to center court as he yelled his way to victory in the first two sets and often cheered Sonego's mistakes.

Unseeded Sonego mounted a fightback to push the game deep into a fourth set but faltered in the tiebreak.

Shelton wrapped up the match with a booming crosscourt forehand and high-fived his ecstatic father-coach Bryan Shelton, a former ATP title-winner.

"I feel relieved right now. Shout out to Sonego - that was ridiculous tennis," said Shelton.

"It was one of the favorite matches of my career."

A stern test awaits the American upstart, as top seed Sinner was at his brutal best to tear apart De Minaur in the late match and reach his second semifinal in Melbourne.

The early exchanges saw both players flex their muscles with heavy shot-making but there was only going to be one winner when Sinner broke for the first of six times.

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Defeat extinguished local favorite De Minaur's ambitious bid to end Australia's 49-year wait for a men's champion at Melbourne Park since Mark Edmondson's triumph.