The American cut her foot on broken glass at a restaurant shortly after winning her fourth Wimbledon crown in July and has not played since. She had already announced that she would not take part in next week's Pan Pacific Open in Japan.
"While I have continued to make progress in the recovery of my foot injury, unfortunately I am still not ready to compete at the upcoming Toray Pan Pacific Open in Tokyo and China Open in Beijing," Williams said in a statement.
"These are both fantastic events with loyal fans that I hope to be able to compete in next season. In the meantime I am focused on my rehab program and remain optimistic to return to competition this season." The 4.5 million dollar China Open gets under way in Beijing on October 2.