The final four at WTA Championships, Doha

DOHA, Qatar - With an ace on match point, Kim Clijsters defeated Victoria Azarenka in a competitive three-setter, 64 57 61, and locked in the final four line-up at the WTA Championships - Doha 2010. Clijsters, Samantha Stosur, Caroline Wozniacki and Vera Zvonareva will be in the semifinals.

After losing an incredibly tight 65-minute second set it was all Clijsters in the third, as she needed just 26 minutes to prevail, her ninth win in a row on the WTA (she went 7-0 to win the US Open and also won her first match here).

"It's a matter of time. It's work, and I know I'm going to improve. I just need more time," Azarenka said after the match. "Next year I'm going to be stronger."

Clijsters is now 2-0 in her group, as is Zvonareva; the two will meet on Friday, with the winner to finish No.1 in their group and the other No.2. Azarenka and Jelena Jankovic, both 0-2 so far, will also play to determine No.3 and No.4.

The Top 2 in the other group were settled, with Stosur No.1 and Wozniacki No.2. Elena Dementieva and Francesca Schiavone will play for No.3.