The third seed recovered from an early setback in the deciding set before eventually prevailing 3-6, 6-4, 6-3 in a tense baseline battle at Flushing Meadows.
The contest lasted two hours and 20 minutes, with the 32-year-old extending her unbeaten record against Navarro to five victories.
“It was really tough,” Pegula said after a match featuring nine breaks of serve.
“It was physical, humid. I wasn’t exactly serving my best and I was fighting a lot of demons out there today.”
Pegula will now face Sabalenka at Arthur Ashe Stadium on Thursday, with the Belarusian aiming to maintain her grip on the tournament after winning the last two editions. Sabalenka overcame Pegula in the 2024 final before repeating the feat in the semi-finals a year later.
The American, who has collected two titles during 2026, entered the tournament as one of three players capable of displacing Sabalenka at the top of the world rankings. However, Pegula would have to win the US Open and secure a maiden Grand Slam crown to have a route to No. 1.
That battle could be resolved before the pair meet, though, as world No. 2 Elena Rybakina can take the top spot outright by defeating China’s Zheng Qinwen in their quarter-final on Wednesday.
Navarro, a former world No. 8, had been rebuilding her career after taking an extended break to prioritise her health. She won her first title in over a year at Strasbourg in May.
