Williams told organizers on Wednesday she had aggravated a left wrist injury that forced her out of tournaments late last year and from the Hopman Cup mixed teams competition in Perth last week.

The former top-ranked Williams has never won the Australian Open, her best result being a loss in the final to her younger sister Serena in 2003.

The five-time Grand Slam singles titlist was ousted in the first round at Melbourne Park last year by Bulgaria's Tsvetana Pironkova.

Williams had an injury plagued 2006, only playing two matches after Wimbledon and finishing the year at No. 48 in the rankings.

Henin-Hardenne withdrew last week due to undisclosed personal reasons, while Russians Svetlana Kuznetsova and Nadia Petrova are doubtful starters after withdrawing from a warmup event in Sydney this week.

On the men's side, No. 2-ranked Rafael Nadal withdrew from the Sydney tournament with a groin problem, along with No. 3-ranked Nikolay Davydenko, who retired with a foot injury.