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Sabalenka, who has won two matches in a row in the round-robin Group Steffi Graf, is on the verge of qualifying for the semi-finals. Gauff and Pegula, who have one win each, also remain in contention for the last four.

"(Pegula) is an incredible player. She always pushed me to the limit... I was thinking, I'm gonna go after my shots, stay aggressive, put all of that speed back on her and hope that I get my chance," four-time Grand Slam champion Sabalenka said.

Sabalenka got the first break with a chip across the court to go 4-2 up, but Pegula soon broke back to make it 5-4. Pegula saved three set points in the next game, but a persistent Sabalenka clinched a decisive break with a powerful forehand from the baseline.

The U.S. Open champion, who had beaten Paolini on Monday, grew frustrated as she made 13 unforced errors, nearly twice as many as Pegula, as the American got two breaks to build a 5-2 lead before saving two break points to secure the second set.

Sabalenka struggled with double faults as Pegula broke early in the third set. However, the Belarusian responded with returns near the sidelines to get two straight breaks, building a 4-2 lead that proved unassailable for Pegula.

Two-time Grand Slam winner Gauff, who made 17 double faults when she lost to fellow American Jessica Pegula in her first game in Group Steffi Graf on Monday, committed only three double faults this time as she dominated the eighth seed earlier in the evening.

The 21 year-old American took just over 10 minutes to build a 3-0 lead in the first set before Paolini went through a nine-minute battle to fend off three break points and win her first game.

Paolini got a break but Gauff drew the Italian into backhand rallies and won points with precise cross-court shots to claim the next game and take a 5-3 lead before holding to win the set.

The French Open champion's strategy of making Paolini run constantly from one side of the court to the other paid off again when Gauff got back-to-back breaks to go 5-2 up in the second.

She secured victory with a powerful serve that Paolini could only hit into the net. Paolini was eliminated from the tournament with two straight defeats.

"I knew today’s win was important to keep myself in the tournament. If I lost, I would have been out," world number three Gauff said.

World number two Iga Swiatek will take on Amanda Anisimova on Thursday, while Elena Rybakina will face Madison Keys in Group Serena Williams.