DOHA: Defending champion Venus Williams and sister Serena will clash for the 23rd time in their careers in the final of the $4.55 million WTA Championships.

Venus, the world No 7, defeated Serbia’s Jelena Jankovic 5-7, 6-3, 6-4 in her semi-final while 2001 champion Serena, the new world No 1, reached the final when Caroline Wozniacki was forced to retire. Danish teenager Wozniacki, who came into the tournament carrying a left thigh strain and who had struggled with cramps in the round-robin stage, was 4-6, 1-0 when a stomach strain forced to her to quit.

Serena and Venus will be far from fresh for the final. Serena played her semi-final with a tightly-bandaged left thigh — as did Wozniakci — while Venus needed treatment on her sore left knee in the first set of her clash against Jankovic. With fitness worries on her mind, Serena earlier on Saturday pulled out of next weekend’s Fed Cup final between the US and Italy.

For the 29-year-old Venus, it’s been a remarkable year. She only squeezed into the last four having lost two of her three group games and arrived in the semi-finals having spent five hours more on court than her Serbian opponent. She was also forced into a fourth successive three-setter.

Williams’s win took her career record with Jankovic to 5-5. Jankovic was the eighth and last qualifier for this end of season money-spinner.