The world number one had endured ‌a frustrating build-up to the year’s ‌final major but has hit her stride at ‌Flushing Meadows and she slammed her foot ‌on the gas in the second set against the home-crowd favourite, sealing victory with a backhand ‌winner.

She will next play either Ukrainian ⁠11th seed ‌Marta Kostyuk or the Czech Republic's Wimbledon champion Linda Noskova.

"What an ​incredible player she is approaching the net, what a great returner," said ​Sabalenka. "Very brave, you can see how focused she was. It was really challenging playing ⁠her, especially here."

Any ​expectation of a one-sided contest between the top-ranked Sabalenka and world number 96 Townsend quickly disappeared as they traded two breaks apiece ‌in the opening four games at Arthur Ashe Stadium.

Sabalenka broke again in the seventh game, firing a forehand winner to seize the advantage, but Townsend responded immediately by breaking to love.

The Belarusian held firm when it mattered, however, saving a break point with an unreturnable serve before closing out the ‌opening set in the 10th game.

Townsend tamed ​Sabalenka's fearsome serve to move 3-1 ‌up in the second set but a double fault handed the break straight back and shifted the momentum decisively.

Sabalenka then sprinted through the final four games to ⁠book her spot ⁠in the last ‌eight.