Serena Williams of the U.S. poses with her trophy after winning the women's singles final match against Victoria Azarenka of Belarus at the U.S. Open tennis tournament in New York's Central Park, September 9, 2013. REUTERS/Keith Bedford

(Reuters) - Women's world number one Serena Williams has pulled out of next week's Pan Pacific Open in Tokyo citing fatigue, Japan's Kyodo news agency reported on Thursday.

"I'm disappointed to have to withdraw from the Pan Pacific Open, which I was very much looking forward to playing this year," the American was quoted as saying.

"Unfortunately with the number of matches I have played throughout the summer I need more time to properly recover."

Williams, who won her fifth U.S. Open singles title this month, was the latest high-profile withdrawal from the September 22-28 tournament after Russian Maria Sharapova also pulled out last week to recover from a right shoulder injury.

(Reporting by Sudipto Ganguly; Editing by John O'Brien)