MELBOURNE, AUSTRALIA (AP) - Venus Williams withdrew from the Australian Open on Monday, prolonging her absence from the tennis tour because of an autoimmune disease that can cause fatigue and joint pain.
The seven-time Grand Slam title winner announced on Twitter and her website that she wouldn't play in the year's first major tournament, which starts next week. She added, though, that she plans to be back in action next month.
Williams hasn't played competitively since Aug. 29 at the U.S. Open. Two days later, she pulled out of that tournament, revealing that she'd been diagnosed with Sjogren's syndrome.
"I regret to announce that I am withdrawing from the 2012 Australian Open. After several months of training and treatment, I am making steady progress to top competitive form. My diet and fitness regimen have allowed me to make great strides in terms of my health and I am very close to being ready to return to WTA competition," Williams said in a posting on her website Monday. "I have every intention to return to the circuit in February."
Australian Open tournament director Craig Tiley said Williams was "very disappointed" that she was not able to play in Melbourne.
"She had hoped she'd be further along in her preparation but is not quite ready for Grand Slam competition," Tiley said in an email to The Associated Press. "She's an amazing champion and she's had a tough year battling illness and injury. We wish her all the best and look forward to seeing her back in Australia soon."
Top-ranked Caroline Wozniacki, a former doubles partner of Williams, said the American's health must come first.
"She's been unlucky with the virus thing," Wozniacki said after her second-round win Tuesday at the Sydney International. "I'm not completely sure what it is exactly, but the most important thing is the health.
"Tennis, it's a game. I'm sure she'll come back and fight and try to come back to the top again. But most of all, the most important thing is that you're healthy. Hopefully she'll be 100 percent healthy by February."
The 31-year-old American is a former No. 1 who is 100th in this week's WTA rankings. She's dealt with a series of health problems, including a hip injury that forced her to withdraw from last year's Australian Open, and a left knee injury that kept her on the sideline between Wimbledon and the U.S. Open in 2010.
Since reaching the semifinals at the 2010 U.S. Open, Williams has played only 11 matches.
After winning her opener at Flushing Meadows in August _ which was Williams' first match in two months _ she withdrew shortly before her second-round match there.
At that time, she described the way she'd been feeling this way: "It was just energy-sucking, and I just couldn't play pro tennis."
Her younger sister Serena, whose 13 Grand Slam titles include five at the Australian Open, badly sprained her left ankle at a tournament in Brisbane this month. It's not clear whether Serena will be able to play at the Australian Open.