Serena will sit out the rest of the year

New York: Serena Williams has been sidelined for the rest of this year after re-injuring her right foot from over-training.

The American world number two pulled out of next week's WTA Championships in Doha and next month's Fed Cup final between the United States and Italy in San Diego after having further treatment on her foot on Monday.

"It is with deep frustration that I am withdrawing," Williams said on Tuesday on her website. "Pushed by my desire to return to competition, I trained too hard too soon and re-tore the tendon in my foot.

"As a result, yesterday morning I had to have another procedure to repair it. I thank everyone for their continued support during this difficult time and look forward with strength and determination to getting back on the court."

The American, who has not played since she won her 13th grand slam at Wimbledon, had her initial surgery after cutting her foot on broken glass at a restaurant in July.