Venus Williams vows return to tennis from chronic illness

NEW YORK (Reuters) - Venus Williams fully expects to return to tennis despite being diagnosed with an autoimmune disease that causes fatigue and led to her shocking decision to withdraw from the U.S. Open.

"Absolutely, absolutely. The good news for me is now I know what is happening after years of not knowing. I feel like now I can move on," the seven-time grand slam winner told ABC's "Good Morning America" program on Thursday.

"I feel really positive about getting back on the court and at least being able to feel normal. I feel like now I can get better."

The five-time Wimbledon champion said she felt some relief in finally being diagnosed so that she can now focus on getting better and resuming her career.

"The best thing that could have happened for me this summer was to feel worse so I could feel better," she said.

Williams, whose sister Serena is among the favorites to win this year's U.S. Open, said her problems with fatigue had puzzled doctors for some time after initially it was felt she had a kind of asthma.

"I had trouble with stamina. I had swelling and numbness and fatigue, which was really debilitating. I just didn't have any energy and it's not that you don't have energy; you just feel beat up," she said.

The two-time U.S, Open champion informed officials of her withdrawal from the tournament less than an hour before she was due to face Germany's Sabine Lisicki in the second round.

"I had a tough practice, I was just sitting there and it was taking an effort just to lift my arms. I didn't feel like I had to put myself through that," said Williams.

"I just felt like, 'OK, I could walk out on the court. I'm a tough woman, I'm a tough athlete, I've played through a lot of things.' But what kind of match it would be? It was a tough decision, but at the same time I've had to come to accept what I'm going through."

(Reporting by Simon Evans in Miami; Editing by Frank Pingue)