Wimbledon champion Venus Williams has withdrawn from next month's Toyota Princess Cup in Tokyo, apparently to avoid a possible clash with her sister Serena.
Venus decided to withdraw from the event after discussing the matter with her family, said a Toyota Princess spokesman, quoting a WTA statement.
The WTA notified the tournament organisers earlier this week, the spokesman said.
The decision, he said, was unfortunate because a possible match between Venus and her younger sister, Serena, would have been the highlight of the tournament.
Serena, the Toyota Princess Cup defending champion, is scheduled to play in the September 17-23 tournament as planned, along with fellow American Jennifer Capriati who is the world's second-ranked player.
Capriati won the year's first two grand slams in Melbourne and Paris.
Spanish veteran Arantxa Sanchez Vicario and Yugoslavia's Jelena Dokic will also participate. Japan's ace Ai Sugiyama, currently the top-ranked WTA doubles player, and former world number one Martina Navratilova will enter the doubles draw.