World number two Li Na of China has been ruled out of this year's US Open with a knee injury.
Na, 32, who won the Australian Open earlier this year for her second Grand Slam title, has targeted a return to action in late September.
The BBC quoted her, as saying on a Facebook post that she had been struggling with her injured knee since March this year, and that she felt that it was not in order for her to play at the highest level.
The US Open starts on 25 August in New York and Li will miss the WTA events in Montreal and Cincinnati as well.
Na said that her medical team has advised her to take some time off to rest her knee.
