Soon-to-be world number one Serena Williams should know by year's end whether she will be barred from the Australian Open over her outburst at the US Open, the WTA's chief executive said Saturday. The result of an International Tennis Federation probe was likely to be known in the coming months, Stacey Allaster told a press conference Saturday on the sidelines of the China Open. Williams drew a 10,000-dollar fine in Flushing Meadows for her verbal assault of a female line judge after she called a foot fault at a key point in a semi-final loss against eventual champion Kim Clijsters. 'It is under investigation. It is ongoing,' said Allaster, who took over from Larry Scott during the summer. 'It would be safe to assume a decision will be taken before year-end. 'Serena has acknowledged the incident as a mistake. It's something she's not proud of, and she's apologised for that,' said the Canadian. Williams, 28, is being investigated by the ITF's Grand Slam Committee and could face bans from one or more of the four major tournaments. The next Slam, the Australian Open, begins in January. 'I think all of us would love to have it resolved sooner rather than later,' said Allaster. 'It would be in the best interests for the sport and definitely the best interests for Serena.' Williams lost in the third round of the China Open but is nevertheless mathematically assured of regaining the top WTA world ranking from Russia's Dinara Safina when the new list is issued on Monday. 'I'm a very passionate player. I just do the best I can in the best manner I can,' the 11-time Grand Slam winner said Thursday after her loss to Russia's Nadia Petrova, telling reporters she had taken the US Open debacle to heart. 'Obviously I would be not smart if I did the same thing. I think it's important for people to learn from things that they've done in the past and I feel like I've completely learned and I would never do the same thing.' 