TOKYO, Sept. 19 (Xinhua) -- World No.1 Serena Williams of the United States has pulled out of the upcoming Pan Pacific Open in Japan, according to the organizers Thursday.

Serena said she has played through the summer and needs more to recover from fatigue, adding she was disappointed to withdraw from the event, local media reported.

Earlier last week, Russian Maria Sharapova said that she was skipping the tournament so as to recover from a right shoulder injury.

The Pan Pacific Open will be held in Tokyo from Sept. 22 to 28.