It would end two tie-breaks later with the Belarusian walking off court into her second Grand Slam final of the season.
Soaking up the energy of the home crowd, the 17th seed unleashed a barrage of winners and broke Sabalenka three times to open the match 6-0.
Keys broke the Australian Open champion for a fourth time for a 2-1 lead in the second, leaving a frustrated Sabalenka screaming and smashing her racquet.
But with Keys serving for a place in the final the Sabalenka who players fear finally appeared.
For Keys, who played in the last all-American women's final in 2017, losing to Sloane Stephens, is was a missed opportunity to return to her home final that left her in tears.
Persons:
Sabalenka, Madison Keys, Mike Segar, Aryna Sabalenka, Coco Gauff, Karolina Muchova, Arthur Ashe, Keys, Sloane Stephens, Steve Keating, Peter Rutherford
Organizations:
Tennis, Madison, U.S, REUTERS, Madison Keys, American U.S, Thomson
Locations:
Flushing Meadows , New York, United States, Belarus, American, Belarusian, New York