The equation could not be simpler -- whoever performs best out of Russian Dinara Safina and American Serena Williams at next week's WTA Championships in Doha will end the year as world number one.

To have the battle for No.1 going to the wire is a dream scenario for women's tour chiefs and the Qatari tennis authorities who paid $42 million to stage the season-ending event for three years until it moves to Istanbul in 2011.

If both players go out at the same stage the number one ranking will probably be decided by who wins most round-robin matches, which are each worth 160 ranking points.

Sunday's draw appeared to hand the advantage to 23-year-old Safina as she was placed in the easier of the two four-women groups that will be contested at the Khalifa Tennis Centre on the shores of the Persian Gulf.

Safina, who briefly lost the world number one ranking in Beijing only to grab it back just in time for Doha due to a quirk of the rankings system, has struggled to win over the critics who say she does not deserve top spot.

The Russian will be determined to do better than last year in Doha when she failed to win a match.

Serena, who claimed the number one spot from Safina at the China Open earlier this month, will once again find herself a handful of points behind the Russian when the latest world rankings are published by the WTA on Monday.

The American is also in the much tougher Maroon Group in Doha where she must play sister Venus, the defending champion, and formidable Russians Svetlana Kuznetsova, the French Open winner, and Olympic gold medallist Elena Dementieva.

Eleven times Grand Slam champion Serena arrives a whisker behind despite winning the Australian Open and Wimbledon, though it is her reputation as much as what she feels is her rightful place at the top of the rankings she is desperate to restore.

While Serena and Safina joust for the No.1 spot there is plenty of other interest in the tournament and not just in singles.

Jankovic too will like to catch up on the points.

Breakthrough years for Wozniacki and Azarenka have underlined the new depth in women's tennis and, with former world number ones Maria Sharapova, Kim Clijsters and Justin Henin, who will make her comeback in January, watching from afar, the health of the game looks rosy.