US Open PIX: Sabalenka beats Keys; sets up Gauff final

Images from the US Open women's semi-finals at the USTA Billie Jean King National Tennis Center, Flushing Meadows, New York, on Thursday.

Second seed Aryna Sabalenka staged a Grand Slam fight back for the ages to rock Madison Keys 0-6, 7-6(1), 7-6(5) on Thursday to deny the home crowd the all-American US Open women's final they had been dreaming of.

Sabalenka will now try to heap even more disappointment on US tennis fans in Saturday's final when she takes on Coco Gauff, who beat Karolina Muchova 6-4, 7-5 in a match halted for nearly an hour when an environmental activist glued his feet to the floor of Arthur Ashe Stadium.

A giddy capacity crowd waving US flags were ready to celebrate getting the final they hoped for when Keys bageled the Belarusian in the opening set and was 5-3 up in the second, serving for a spot in the final.

But Sabalenka had other ideas.

Her fight back began by breaking Keys to get back to 5-4 and continuing the match. It would end two tie-breaks later with the Belarusian walking off court into her second Grand Slam final of the season.

In a contest featuring two of the biggest hitters in the women's game, it was Keys coming out with guns blazing to dominate the Belarusian, who will take over as world number one when the rankings are updated on Monday.

Soaking up the energy of the home crowd, the 17th seed unleashed a barrage of winners and broke Sabalenka three times to open the match 6-0.

Keys broke the Australian Open champion for a fourth time for a 2-1 lead in the second, leaving a frustrated Sabalenka screaming and smashing her racquet.

But with Keys serving for a place in the final the Sabalenka who players fear finally appeared.

The Belarusian got her first break of match as the set went to a tie-break which she won 7-1, sending the contest to a third set that minutes earlier no one saw coming.

With the tension rising so did the quality of the match, the players trading breaks in a tight third set that came down to a super tie-breaker which Sabalenka again dominated 10-5.

 Gauff beats Muchova to reach first US Open final

American Coco Gauff beat Karolina Muchova 6-4, 7-5 to reach her first US Open final on Thursday after the match was halted for nearly an hour when an environmental activist glued his feet to the floor of Arthur Ashe Stadium.

Gauff, who had beaten Muchova in the Cincinnati final last month to claim the biggest title of her career, fed off the energy of the home crowd to get past the Czech once again.

"Some of those points, it was so loud and I don't know if my ears are going to be okay," Gauff said. "I grew up watching this tournament so much so it means a lot to me to be in the final. A lot to celebrate but the job is not done."

Gauff, the sixth seed, will next face the winner of the other semi-final between compatriot Madison Keys and Belarusian second seed Aryna Sabalenka.

The match was delayed by roughly 50 minutes early in the second set due to a protest by four spectators.

The USTA said three of the four were escorted out of the stadium without incident but a fourth "affixed their bare feet to the floor of the seating bowl".

Gauff swept the first three games of the opening set and broke her opponent again in the sixth.

Muchova, this year's Roland Garros runner-up, capitalized on some mistakes by the 19-year-old and broke straight back in the seventh, raising her level from there to break Gauff again in the ninth.

The Czech's good work went to waste, however, as she committed a trio of unforced errors in the 10th game, allowing Gauff to break to love and take the set.

After a routine hold by Gauff to open the second set, shouts were heard from high up in the stands and both players sat on their benches as security staff members quickly moved to quell the disruption.

As the delay stretched on both players left the court as police officers surrounded the remaining protester before removing him from the venue with his hands behind his back.

After the players returned they warmed up again on court before resuming play, neither appearing rattled by the incident.

Muchova double-faulted to help Gauff break in the eighth game but saved match point in the next game before breaking the American’s serve to keep the match going.

Muchova saved four more match points in the 12th game but Gauff would not be denied, surviving a 40-shot rally on the penultimate point with a forehand winner before cheering with delight as her opponent sent a backhand past the baseline on the sixth match point.

Muchova gave credit to her opponent but told reporters that she was disappointed in the quality of her own play on Thursday.

"I was not feeling it from the start until the end," she said. "I'm pretty sad about the outcome, that I didn't put the best out of me on the court. Yeah, just kind of sad about the performance."