Both the Williams sisters won their round-robin matches on Wednesday at the season-ending Sony Ericsson Championships in Doha.
Third-seeded Serena saw her first action of the week and moved to 1-0 in the four-player Maroon Group with a 6-4 6-1 victory over Russian Dinara Safina, who is a disappointing 0-2 already this week. Safina lost to Venus Williams on Tuesday.
In another Maroon Group match, seventh-seeded Venus defeated fifth-seeded Olympic gold medalist Elena Dementieva 6-4 4-6 6-3. Venus is now 2-0 and appears well on her way to the semifinals, while Dementieva fell to 0-1.
On Thursday the Williams sisters will play each other. Serena is 9-8 all-time against her older sister, including a 2-1 record this year. The two have never met at the season-ending Championships.
Besides the clash of Venus and Serena Williams, the Sony Ericsson Championships will feature the following matches on Thursday: Jelena Jankovic vs. Svetlana Kuznetsova, Dinara Safina vs. Elena Dementieva.