Williams sisters to clash in Doha

Serena Williams will take on elder sister Venus in the group stages of the season-ending Tour Championships in Doha, which begin on Tuesday.

The Americans have been drawn in the Maroon Group, along with Russians Elena Dementieva and Dinara Safina.

Serbians Jelena Jankovic and Ana Ivanovic, and Russians Svetlana Kuznetsova and Vera Zvonareva, make up the White Group.

Two players from each group will advance to the semi-finals.
The tournament, which takes place in Doha for the first time, is without its defending champion following the retirement of Justine Henin in May.

Australian Open champion Maria Sharapova is also absent because of a shoulder injury.

Serena Williams claimed the world number one ranking after winning the US Open in September, but Jankovic has since regained the position and will end the year at the top of the rankings no matter what the result in Doha.