The American, who has not played competitively since she defeated her sister Venus in the All England Club final in July, underwent left knee surgery in August.

Serena confirmed her withdrawal from next month's year-ending WTA Championships in Los Angeles, thereby bringing a premature end to her 2003 season.

"I really miss playing tennis and I can't wait to come back and compete, however, I feel that I need more time to prepare and get myself in the best shape possible," the world number three said in a statement.

"I'd like to thank all of the fans who have been so supportive. I'll be back... better than ever."

Venus has also been sidelined since Wimbledon due to an abdominal strain but is expected to make her return at the Philadelphia tournament later this month.

The duo have also been mourning the death of their elder sister Yetunde Price, who was fatally shot in a Los Angeles suburb last month.

Serena has slipped to third in the world rankings after being dethroned from the top spot in August by Belgian Kim Clijsters.

The 22-year-old also won the Australian Open in January before her triumph at Wimbledon, which took her Grand Slam tally to six.