Former world number one Serena Williams [ Images ] has pulled out of next month's Hopman Cup team event.

Williams told organisers of the Perth event that she wants to concentrate on defending her title at the Australian Open [ Images ] in Melbourne [ Images ] which begins on January 19.

The world number three, the winner of six Grand Slam titles, will be replaced in the U.S. Hopman Cup team by Lindsay Davenport [ Images ], tournament director Paul McNamee told reporters on Monday.

World number five Davenport will partner James Blake [ Images ] for the defending champions at the January 3-10 team event.

"Serena regrets not being able to come back and defend her title but we have a wonderful replacement in Lindsay Davenport," said McNamee, who is also an Australian Open director.

The United States remain the top seeds ahead of Australia [ Images ] despite the loss of Williams.

Neither Williams nor her elder sister Venus have played since Wimbledon [ Images ], in July, a championship Serena won.

Serena, 22, had knee surgery in August. Venus is planning to return in Melbourne after a long lay-off with an abdominal tear.

The Australian Open will mark the first tournament appearance for Serena and Venus since their sister Yetunde Price was shot dead in a Los Angeles suburb in September.