New York, New York - Jessica Pegula staged an astonishing recovery from a set and a break down to defeat Karolina Muchova and reach her first Grand Slam final at the US Open tennis tournament on Thursday.

The sixth-ranked American came through 1-6, 6-4, 6-2 and will take on world number two and Australian Open champion Aryna Sabalenka in Saturday's championship match.

Sabalenka reached her second successive US Open final by seeing off another American, Emma Navarro 6-3, 7-6 (7/2).

"I thought I was lucky to still be in it," admitted Pegula after seeing Czech opponent Muchova miss an easy chance to go 3-0 up with a double break in the second set.

"She made me look like a beginner. She was destroying me and I was about to burst into tears, but it all came down to small moments."

"I don't know how I turned that around."

Pegula has now won 15 of 16 matches on the US summer hard court swing which saw a title in Toronto and defeat in the Cincinnati final to Sabalenka.

"It's a chance for revenge, but she'll be tough to beat," said Pegula.

Muchova saved three break points in the third game of the first set, which sparked a rapid collapse by Pegula.

The 30-year-old American dropped serve in the fourth and sixth games and lost a set for the first time in the tournament.

Muchova's all-court game yielded 11 winners to her opponent's three as the opener was wrapped up in just 28 minutes.

It was a severe comedown for Pegula, who had knocked out world number one Iga Swiatek on Wednesday to reach her first Grand Slam semi-final after losing all six of her previous last-eight matches.

Muchova then broke for a 2-0 lead in the second set, racking up a seventh game in a row before Pegula stopped the rot.

That suddenly reinvigorated the American, who went 4-2 ahead before being pulled back to 4-4 but then leveled the semi-final when Muchova double-faulted on set point.

Pegula sprinted to a break up at 3-0 in the decider and then 5-2 after a seventh game which stretched to almost 10 minutes.

The last of Muchova's 46 unforced errors sealed her fate.

World number two Aryna Sabalenka reached a second successive US Open final earlier in the day when she defeated a battling Emma Navarro to move one win away from her third Grand Slam title.

Double Australian Open champion Sabalenka triumphed over the 13th-seeded American 6-3, 7-6 (7/2).

Navarro, playing in her first semi-final at the majors, went down fighting, however, when she clawed her way back from 3-5 down in the second set to take her chances in a tiebreak.

Sabalenka sent down 34 winners to the 13 of the 23-year-old American in the tie.

"Guys, now you're cheering for me. Wow. It's a bit too late," Sabalenka told the Arthur Ashe Stadium crowd. "I don't really care who I face in the final because tonight I heard the crowd cheer for my opponent."

She added: "I was like 'Aryna stay focused – not this time, guys.'"

The Florida-based Belarusian, runner-up to Coco Gauff in New York last year, called on her raw power to secure the first set, nullifying Navarro's smart use of the angles.

Although an early break was canceled out by the American, the 26-year-old edged ahead again in the sixth game before securing the opener on the back of 16 winners, twice as many as Navarro.

Sabalenka stretched to a 3-2 lead with a break in the second set with Navarro having to fend off more break points to avoid slipping to a 2-5 deficit.

That breathed new life into her challenge and she broke Sabalenka when her rival served for the match, pulling level for 5-5.

She even enjoyed a mini-break in the tiebreak before Sabalenka stormed back for victory.