Australian Open champion Kim Clijsters has withdrawn from Wimbledon because of a foot injury.

The second-ranked Belgian, who was seeded No. 2 yesterday, said she had to pull out of the grasscourt grand slam after re-injuring her right foot at the Unicef Open in the Netherlands on Tuesday.

Clijsters says "at this moment I feel frustrated that it has to happen now before one of my favorite tournaments. I've always enjoyed being a part of the Wimbledon atmosphere but I have no other choice now but to rest, recover and to not play tennis for a few weeks."

The two-time US Open winner hurt her right ankle in April while dancing barefoot at her cousin's wedding. She played at the French Open but lost in the second round.

Because of the Belgian's withdrawal, defending champion Serena Williams was bumped up to No. 7 in the Wimbledon seedings, a position that will allow her to avoid playing the highest-ranked players until at least the quarterfinals.

Her sister Venus is lurking down at 23rd, after the All England Club's seedings committee met yesterday.

Serena was top of the WTA rankings when she won her fourth Wimbledon title last year, her 13th major singles crown in all, but is now down at 26 after 11 months out through injury and health woes.

The 29-year-old American required surgery on her foot after slicing it open on broken glass in a Munich restaurant last July and then needed emergency treatment in February for potentially life-threatening blood clots on her lungs. She returned to action this week at Eastbourne after taking a wildcard.

Hip injuries

Venus, who has won five Wimbledon singles titles but is now ranked 33, also made a comeback in Eastbourne after not playing since the Australian Open because of abdominal and hip injuries.

The sisters, who between them have won nine of the last 11 singles titles at Wimbledon, were upgraded at the discretion of the All England Club to ensure "a balanced draw".

The rest of the seedings follow the WTA rankings with Denmark's world No. 1 Caroline Wozniacki topping the draw.

The men's seedings, based mainly on the ATP rankings but which can be tweaked to reflect grasscourt form, have a top four of defending champion Rafael Nadal of Spain, Serbia's Novak Djokovic, Swiss six-time champion Roger Federer and Andy Murray of Briton.

American Andy Roddick, three time a runner-up, has earned the eighth seed despite a current ranking of 10 which means he will avoid the "big four" until the quarterfinals.

Frenchman Jo-Wilfried Tsonga has also been shunted up to 12th from a ranking of 19 after his run to the Queen's Club final where he lost to Murray.