A farewell letter from tennis ace Li Na announcing her retirement ended speculation about her future on Friday.

Although the 32-year-old has been unable to overcome a severe knee injury, the two-time Grand Slam winner's achievements have brought her widespread and lasting acclaim.

"It's a great pity (that Li is retiring)," said Xiao Tian, deputy director of China's State General Administration of Sport. "We respect her decision and wish her well for the future."