Serena Williams reaches WTA Finals semis as Halep levels match against Ivanovic

Simona Halep of Romania reacts during a match against Ana Ivanovic of Serbia at the Women's Tennis Association (WTA) finals round robin match in Singapore on Oct 24, 2014. -- PHOTO: AFP
Simona Halep of Romania reacts during a match against Ana Ivanovic of Serbia at the Women's Tennis Association (WTA) finals round robin match in Singapore on Oct 24, 2014. -- PHOTO: AFP
Ana Ivanovic of Serbia celebrates a point against Simona Halep of Romania during their WTA Finals singles tennis match at the Singapore Indoor Stadium on Oct 24, 2014. -- PHOTO: REUTERS
Ana Ivanovic of Serbia celebrates a point against Simona Halep of Romania during their WTA Finals singles tennis match at the Singapore Indoor Stadium on Oct 24, 2014. -- PHOTO: REUTERS
Serena Williams of the US hits a return to Simona Halep of Romania during session 3 of the WTA Finals singles tennis match held at the Singapore Indoor Stadium on Oct 22, 2014. -- ST PHOTO: KUA CHEE SIONG
Serena Williams of the US hits a return to Simona Halep of Romania during session 3 of the WTA Finals singles tennis match held at the Singapore Indoor Stadium on Oct 22, 2014. -- ST PHOTO: KUA CHEE SIONG

SINGAPORE (AFP) - Tennis' world No. 1 Serena Williams reached the WTA Finals semi-finals on Friday, when Simona Halep won the second set of her match against Ana Ivanovic.

Halep earned a reprieve for Williams, whom she stunned 6-0, 6-2 on Wednesday, and guaranteed top spot in the Red Group round robin when she took the second set 6-3.

Ivanovic won the first set but the result of the match is now immaterial to the final standings.

Win or lose the deciding set, Halep will play White Group runner-up Agnieska Radwanska in Saturday's semi-finals, while Williams takes on Caroline Wozniacki, who won all her matches against Radwanska, Petra Kvitova and Maria Sharapova.