China's Li Na announces her retirement from tennis

BEIJING, Sept 19 (Reuters) - China's Li Na, Asia's first grand slam singles title winner, announced her retirement from tennis on Friday. "It has been a difficult year, and I have had to face a lot of things, such as making the decision to end my professional tennis career," Li said on her official Weibo microblog. (Reporting by Ben Blanchard, Li Hui and Hou Xiangming)