The top two seeds and the bottom two seeds face off to secure a spot in tomorrow’s championship match.
Karolina Pliskova raised her game when it mattered to claim victory over Halep and earn a semi-final clash with Barty at the 2019 WTA Finals.
Barty advanced to the semi-finals of the WTA Finals with a straight-sets win over Kvitova, while Bencic progressed when Bertens retired.
Elina Svitolina beat Simona Halep in straight sets in confident style to book her place in the semi-finals at the WTA Finals in Shenzhen.
The two household names are set to lock horns at Flushing Meadows on Monday.
Elina Svitolina proved her doubters wrong with a spectacular unbeaten week at the 2018 WTA Finals that may turn out to be career-defining.
The singles final will feature two players who are undefeated thus far this week in Singapore.
Elina Svitolina outsmarted Kiki Bertens in a three set epic to reach the final in Singapore.
Capping off another topsy-turvy year on the WTA tour, the lowest four seeds in the tournament have advanced out of the robin stage.
Sloane Stephens won her third consecutive match at the 2018 WTA Finals to finish top of the group and qualify for the semi-finals.
The Dutch player has reached the semi-finals of the tournament despite being the lowest ranked player in the draw.
In the red group, all matches thus far have gone to three sets, and all four players still have a chance of advancing on Friday.
Elina Svitolina is into the last four of the WTA Finals for the first time after edging Caroline Wozniacki in a dramatic contest in Singapore.
The 26-year-old is the first player to qualify for the semi-finals of this year's season-ending tournament.
The sudden surge in interest surrounding the US Open champion is inevitable, but not necessarily good.
Elina Svitolina leads the white group, but all four players still have a chance of qualifying for the semifinals.
Sloane Stephens produced a stirring fightback in the final set to gain a vital win over Kiki Bertens that edges her closer to the last four.
Angelique Kerber fights past Naomi Osaka in the battle of the grand slam champions to keep her semi-final hopes alive.
Sloane Stephens and Kiki Bertens will play for the top spot in the red group, while Angelique Kerber and Naomi Osaka will play to stay out...
Elina Svitolina moved into pole position in the White Group with an excellent win over Karolina Pliskova.