Serena Williams on Monday said she has not retired from tennis and that the chances of her returning are "very high" after she previously indicated that she would step away from the sport after last month's US Open.

"I am not retired," Williams said at a conference in San Francisco while promoting her investment company, Serena Ventures.

"The chances (of a return) are very high. You can come to my house, I have a court."

Williams, 41, said she was "evolving away from tennis" in an essay in August and, while she did not confirm the US Open as her farewell event, she was given lavish tributes before each match in New York and waved an emotional goodbye after losing in the third round.

The 23-time Grand Slam champion, who took the tennis world by storm as a teenager and is considered by many the greatest of all time, said not preparing for a tournament after the US Open did not feel natural to her.

"I still haven't really thought about (retirement)," Williams said.

"But I did wake up the other day and go on the court and (considered) for the first time in my life that I'm not playing for a competition, and it felt really weird.

"It was like the first day of the rest of my life and I'm enjoying it, but I'm still trying to find that balance."