Defending champion Aryna Sabalenka and 19th seed Madison Keys will contest the Australian Open final after contrasting victories on Thursday.

In a nerve-jangling late night semifinal, the hard-hitting Keys booked her spot against Sabalenka with an upset 5-7, 6-1, 7-6 (8) win over second seed Iga Swiatek.

Madison Keys hits a return during the women's singles semifinal match between Iga Swiatek of Poland and Madison Keys of the United States at Australian Open tennis tournament in Melbourne, Australia, Jan. 23, 2025. (Xinhua/Ma Ping)

The 2017 US Open finalist blasted seven aces and 36 winners as she moved a step closer to winning a maiden Grand Slam title.

She will start as an underdog in Saturday's final against top seed Sabalenka, who brushed aside 11th seed Paula Badosa 6-4, 6-2 on Rod Laver Arena in one hour and 26 minutes.

She started slowly against her close friend Badosa, trailing 2-0 and 40-love, before warming to her task and taking control. The Belarusian finished with 31 winners to 11 from Badosa and broke four times.

After coming out in an aggressive mood, the 27-year-old Badosa cooled off significantly in her first Grand Slam semifinal and had no answers for Sabalenka's firepower.

The former world No.2 was helpless and unable to reproduce the level from her memorable quarterfinal upset of third seed Coco Gauff.

An unstoppable Sabalenka ran away with the match and she remains well on course for a hat-trick of titles, a feat that only five women have achieved in tournament history with the last being Martina Hingis in 1999.

"It's a privilege if I'm able to put my name into history, it will mean a lot. It will mean the world to me," said Sabalenka, who won her 20th straight match at Melbourne Park.

"I'm so proud of myself. I'm proud of my team that we're able to put ourselves in such a situation."

In the later semifinal, an emotional Keys claimed victory after two hours and 35 minutes in gripping match that finished past midnight.

The 29-year-old American has proven her endurance having battled through four three-set matches en route to her second Grand Slam final.

She had her toughest fight against Swiatek, who had dropped just 14 games in her opening five matches.

The Pole had the edge in a tense first set, but the match flipped when Keys found her range and unleashed a barrage of heavy groundstrokes to level the match.

Swiatek had not dropped a set up to that point of the tournament as a see-saw ensued.

Swiatek had a match point on serve in the 12th game of the third set, but could not close it out as Keys lifted her level to prevail in a pulsating match tiebreak.

"That match was such high level, she played so well. The third (set) was just a battle," Keys said. "To be standing here and be in the final is so exciting."

It was a bitter disappointment for five-time Grand Slam champion Swiatek, whose curse extends in Melbourne having never reached the final of the Australian Open.

Meanwhile, sixth seeds Harri Heliovaara and Henry Patten prevailed in a thrilling men's doubles semifinals with a 6-4, 3-6, 7-6 (7) victory over German fourth seeds Kevin Krawietz and Tim Puetz.

The Wimbledon champions will face third seeds Simone Bolelli and Andrea Vavassori in Saturday's final.

The Italians came from behind to beat Andre Goransson and Sem Verbeek 2-6, 6-3, 6-4 as they reached the final for a second straight year.

The men's singles semifinals will be contested on Friday. Second seed Alexander Zverev plays 24-time Grand Slam champion Novak Djokovic before defending champion Jannik Sinner takes on 12th seed Ben Shelton in the night session on Rod Laver Arena.