WASHINGTON, Jan. 9 (Xinhua) -- Venus Williams of the United States, the seven-time Grand Slam singles champion, announced her withdrawal from the Australian Open on Monday.

The US star are still struggling to return from the autoimmune disease Sjogren's syndrome.

Williams said on her website that she has been making progress and plans to return to WTA Tour play in February.

"I regret to announce that I am withdrawing from the 2012 Australian Open," Williams said. "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. I have every intention to return to the circuit in February," she said.

The 31-year-old also pulled out of the Auckland WTA tournament last week due to the illness.