Jessica Pegula became the fourth American to reach this year's US Open semi-finals on Wednesday by stunning world number one Iga Swiatek of Poland.

Pegula swept past 2022 champion and four-time French Open winner Swiatek 6-2, 6-4 to reach a maiden semi-final at the majors after falling in six quarter-finals.

The 30-year-old will next face Karolina Muchova of the Czech Republic.

If she gets through, that would set-up an all-American title match should Emma Navarro stun world number two Aryna Sabalenka in Thursday's other semi-final.

Victory ended Pegula's run of losing all six Grand Slam quarter-finals in which she had played and extended her streak to 14 wins in 15 matches on US hard courts this summer.

"Finally I can say I'm a semi-finalist. I lost so many of these things," said Pegula after her fourth career win against Swiatek.

"I did everything I could to not get frustrated," she added. "I took advantage of some things she was not doing so well and just rode that momentum."

Pegula raced into a double break in the first set as 2022 US Open winner Swiatek was plagued by mistakes. (AFP)