Beijing  - The head of the WTA said Saturday that it would take weeks for Serena Williams to learn whether she would be banned from one or more future Grand Slams after exploding in anger last month at the US Open.

"It is under investigation and ongoing," WTA chief executive Stacey Allaster said. "It is safe to assume that they [the ITF Grand Slam Committee] will make a decision before year-end.

"All of us would love to have it resolved sooner rather than later. It would be in the best interests for the sport and definitely the best interests for Serena."

Williams was being investigated after what television replays showed as a verbal threat to a line judge who called a foot fault on the American during the crucial closing stage of a semi-final against eventual champion Kim Clijsters.

Reports indicated Williams told the line judge she would ram a tennis ball down the woman's throat.

"She has acknowledged the incident in New York as being a mistake and something that she's not proud of, and she's apologized for that," Allaster said during a visit to the China Open, where Williams lost in the third round to Russian Nadia Petrova.

Williams could be banned from one major or possibly two. Should that happen, it could well be January's Australian Open that she misses.

The 28-year-old was due to take back the number one ranking on Monday from Russian Dinara Safina.

In Beijing, Williams called herself "a very passionate player."

"I do the best I can in the best manner I can," she said. "It's important for people to learn from things they did in the past. I learned and I would never do the same thing." (dpa)