Venus pulls out of US Open

New York - Venus Williams withdrew from the US Open on Wednesday with an unspecified illness, the US Tennis Association said.

Williams, winner of back-to-back titles at Flushing Meadows in 2000 and 2001, had been scheduled to take on Germany's Wimbledon semi-finalist Sabine Lisicki, the 22nd seed, in a second round match on Wednesday afternoon.

Williams was unseeded at the US Open for the first time since her debut in 1997 - when she made it to the final.

She was playing in just her fourth tournament of 2011 thanks to injury and illness.

Since a first-round defeat at Wimbledon, she had withdrawn from WTA events at Toronto and Cincinnati with what was called a viral illness.

After her 6-4, 6-3 first-round victory over Russian Vesna Dolonts on Monday, Williams said the ailment had sapped her energy.

"It was just energy-sucking, and I couldn't play pro tennis," she said.

"It was disappointing, because I had huge plans for this summer of course to improve my ranking," added Williams, who had been sidelined earlier in the season by a hip injury that forced her out of the Australian Open.

Having gotten past Dolonts, Williams had been optimistic that she would be fit enough to go as far as her game would take her in a Grand Slam.

"I think I'll be OK," Williams said, but she apparently spoke too soon.