The sixth-ranked American came through 1-6, 6-4, 6-2 and will take on world No 2 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 No 1 Iga Swiatek on Wednesday to reach her first Grand Slam semifinal 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 levelled the semifinal 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 alnmost 10 minutes.

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