Jessica Pegula rallied after a difficult first set in an emotional US Open semi-final against Karolina Muchova to reach her maiden grand slam final.

Pegula is the oldest American woman in the Open Era to reach her first major final, where she will play Aryna Sabalenka, but she had to do it the hard way in a 1-6 6-4 6-2 in two hours and 13 minutes.

The 30-year-old won her first service game, but Muchova's strength pushed her through the rest of the first set.

Pegula then found herself 2-0 down in the second but dug deep to go on a four-match winning streak and force a decider.

After that, Muchova had no way back, as Pegula got two more breaks in the final set, and she admitted that even she was surprised by the comeback.

"I came out flat, but she was playing unbelievable, she made me look like a beginner," Pegula said.

"I was about to burst into tears because it was embarrassing, she was destroying me.

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

Data Debrief: Pegula's wait is over

It is the second year in a row that an American will play in the women's singles final, with Pegula following Coco Gauff, who won the tournament last time around.

However, by defeating Muchova at the age of 30 years and 193 days, Pegula became the oldest American in the Open Era to reach a maiden grand slam final.

She is also just the third player in the Open Era to win a women's singles semi-final at the US Open after losing the first set 6-1, after Svetlana Kuznetsova (2004) and Victoria Azarenka (2020) – excluding retirements.