Doha, Qatar -- (Sports Network) - The battle for the women's year-end No. 1 will get underway Tuesday at the season-ending $4.55 million Sony Ericsson Championships.

Wimbledon and Australian Open champion Serena Williams and Aussie and French Open runner-up Dinara Safina will decide who finishes the year on top. Safina actually regained the No. 1 ranking from Serena on Monday.

If Serena can win one more match than Safina this week, the American will finish the year No. 1 for the second time in her career. If the two women win the same amount of matches, or Safina wins more, the Russian will finish as the year-end No. 1 for the first time in her career.

Three round-robin matches are on Tuesday's schedule at Khalifa Tennis Complex. A second-seeded Serena will meet third-seeded French Open champ Svetlana Kuznetsova, while fifth-seeded Olympic gold medalist Elena Dementieva will encounter seventh-seeded Wimbledon runner-up Venus Williams and sixth-seeded Victoria Azarenka will face eighth-seeded Jelena Jankovic. Venus defeated Russian Vera Zvonareva in last year's Championships finale.

The exclusive eight-player event caps the WTA Tour season. A four-player White Group features a top-seeded Safina, fourth-seeded U.S. Open runner-up Caroline Wozniacki, Azarenka and the former No. 1 Jankovic. A four-woman Maroon Group boasts Serena, Kuznetsova, Dementieva and the former top-ranked Venus. Serena captured this prestigious event eight years ago. Wozniacki and Azarenka will make their Championships debuts this week.

Round-robin play will determine Saturday's semifinalists, and the champion will be decided in the lucrative final here on Sunday.

An undefeated champ this week would collect $1.55 million.