An emergency bathroom break powered world No 1 Iga Swiatek into a US Open final showdown with trailblazing Tunisian fifthseed Ons Jabeur on Thursday.

Two-time French Open champion Swiatek advanced to the first US Open final of her career after coming from behind to beat Aryna Sabalenka 3-6, 6-1, 6-4 at Arthur Ashe Stadium.

The victory sent the 21-year-old from Poland into a Saturday final with Jabeur, who thrashed France's Caroline Garcia 6-1, 6-3 in Thursday's other semifinal.

Sabalenka, the sixth seed from Belarus, looked poised to create an upset after a dominant first-set performance in which she broke Swiatek three times.

But Swiatek was rejuvenated after a quick dash to the bathroom following the opening set.

"I kind of needed to go," Swiatek said. "For sure I felt lighter. I'm sorry－that's disgusting."

Swiatek also said the break had helped her analyze the flaws in her first-set performance.

"I tried to use that time to think about what to change because I remember when I was younger all I would do in the bathroom between sets after I lost was cry," she recalled.

"But this time I could think about what to change and actually problem solve."

The break did the trick as Swiatek raced through the second set to tie the match and then punished a late collapse from Sabalenka to close out a gutsy victory.

Sabalenka, who was up a break and leading 4-2 in the final set, was left distraught by the defeat. She later appeared in the post-match news conference wearing mirrored sunglasses and a baseball cap pulled over her face.

The 24-year-old is now 0-3 in Grand Slam semifinals for her career and 12-11 in three-setters this year. After Sabalenka broke for a 4-2 lead in the third set, Swiatek took just 17 minutes to surge to victory.

"She was just going for it," said Sabalenka. "She was hitting every ball and putting me under big pressure and playing really aggressively."

On her Grand Slam semifinal losses, Sabalenka said: "My team keeps telling me that I have to be proud of myself, what I have done in the last months.

"But I don't feel that way. I feel like in these three semifinals I had so many opportunities and I didn't use them."

Swiatek has emerged as a dominant figure in women's tennis, with a 37-match winning streak that brought her six titles in one stretch. If she can defeat Jabeur, Swiatek will become the first woman since Germany's Angelique Kerber in 2016 to win two majors in one season.

"I needed to get it together," said Swiatek, who already owns two trophies from the French Open's red clay, including one this June, but never had been past the fourth round on New York's hard courts.

Early lead

Sabalenka looked well placed to reach her first major final as she swept into an early lead against the top seed.

The hard-hitting Sabalenka broke Swiatek three times in the opening set, rattling her opponent's shaky service game and stretching her with an array of powerful groundstrokes.

But Swiatek looked rejuvenated after her bathroom break following the first set and came out for the second all guns blazing.

She broke Sabalenka to love in the opening game and then held twice for a 3-1 lead.

She sealed a further break with a backhand cross-court return of serve to open up a 4-1 advantage as Sabalenka struggled to cope with the change in tempo.

She was broken again in the seventh game, Swiatek tying the match after Sabalenka fluffed an easy volley at the net on set point.

Nevertheless, Sabalenka appeared to have stopped the rot in the third set.

She broke Swiatek in the opening game and then broke again for a 3-2 lead after Swiatek had broken back.

She held serve for a 4-2 lead and the momentum seemed to be with her.

But Sabalenka's game disintegrated from that point on. Swiatek broke her to love to make it 4-4 and then held for a 5-4 lead.

Sabalenka was overrun in the 10th game as Swiatek raced into a 0-40 lead to move to triple match point. A forehand volley at the net saved the first match point, but Sabalenka's 44th unforced error on the next point sealed her fate.

Agencies