NEW YORK, (Reuters) – Serena Williams has pulled out  of the U.S. Open because she is still recovering from surgery  on her right foot, the American world number one said yesterday.

Williams, who won her 13th grand slam at Wimbledon earlier  this year, cut her foot on broken glass at a restaurant in July  and has not played since.

“It is with much frustration and deep sadness that I am  having to pull out of the U.S. Open,” Williams said on the  tournament’s website (http://www.usopen.org/). “My doctors have  advised against my playing so that my foot can heal.”

A three-time winner at Flushing Meadows, Williams absence  will be a blow to U.S. title hopes with her sister Venus, the  world number five, the only other American ranked in the top  40.

With Belgian Justine Henin announcing on Wednesday she  would not be fit to play in the U.S. Open and defending  champion Kim Clijsters losing in Montreal after an injury  scare, the year’s final grand slam is shaping up as a wide open  affair.

“There are still so many other big names out there who can  do well,” said Clijsters, who promised to be in Flushing  Meadows to defend her crown despite a nagging hip injury that  will require an MRI next week. “Serena and Justine are two big  names but there are plenty more out there.

“I don’t look at the draw in that kind of way, I just focus  on my matches and obviously now I am trying to be in the best  shape possible to compete.”

A fan favourite and television ratings grabber, Williams is  sure to be missed especially after her explosive and  controversial exit from last year’s event.

Called for a foot fault in her semi-final against  Clijsters, Williams exploded in an ugly outburst threatening a  line judge during a confrontation that ultimately cost her the  match.

“It doesn’t change much,” said Russian Vera Zvonareva, who  lost to Williams in the Wimbledon final in early July.

“Serena is a great player and is great to watch but there  are so many great players.

“It’s still going to be very tough for everyone.”