Clijsters books semis spot

Qatar - Kim Clijsters beat Victoria Azarenka 6-4, 5-7, 6-1 on Thursday to reach the WTA Championships semi-finals.

Clijsters joined Vera Zvonareva in qualifying for the last four from the White Group, while Sam Stosur and Caroline Wozniacki progressed from the Maroon Group.

Azarenka of Belarus, a replacement for the injured Serena Williams, allowed a 5-3 lead to slip in the second set before winning the next two games to force a decider, but she then appeared to wilt in the heat.

The fourth-ranked Clijsters ran off the first 12 of 14 points on her way to building a 5-0 lead. Azarenka pulled one game back but Clijsters ended the match with an ace to remain perfect in the White Group.