BEIJING, Aug 16 (Reuters) - China's Li Na has pulled out of the U.S. Open starting on Aug. 27 after the recurrence of a muscle injury in her rib area, the China Tennis Association (CTA) said on Thursday.
The 25-year-old, who spearheaded China's breakthrough year in women's tennis in 2006, last played in June at the Wimbledon warm-up tournament in Birmingham, where she sustained the injury during a coughing fit brought about by her pollen allergy.
The world number 21 had planned to make her return to court at last week's Los Angeles Classic but was forced to withdraw from the tournament when the injury flared up again.
"Li Na's injury has not completely recovered so she has to pull out," said CTA spokeswoman Xie Miqing.
Li's compatriot Zheng Jie is also doubtful for the final grand slam event of the year because of the ankle injury that caused her to miss her women's doubles title defence at Wimbledon.
"Zheng Jie is not able to compete for the moment," Xie added. "All the other Chinese players will play at the U.S. Open."