WUHAN, China, Sept. 18 -- China's two-time Grand Slam winner Li Na will announce retirement on Friday, a member of her agent team said on Thursday.

"Li Na will break the news via Sina Weibo on Friday morning and will meet reporters on Sept. 21 (Sunday) in Beijing," said the agent who works for the superstar's agent company, IMG, and asked not to be named.

The scheduled announcement on the Chinese equivalent to Twitter falls on the day that the Asian Games opens in Incheon, South Korea, and the Wuhan Open is inaugurated in Li's hometown.

Speculation has been rife over Li's retirement since the 32-year-old pulled out of the U.S. Open and other hard-court tournaments because of knee injuries.

Fabrice Chouquet, event director of the Wuhan Open, said he was unable to comment because the organizers had not received any formal information about Li's retirement.

"I know Li Na went to Shanghai and Germany in summer to have her knees treated. But I know nothing about whether she is retiring," said Ma Keqin, chief of Hubei Tennis Sport Management Center, a government-backed body in Li's hometown from which she still gets salaries.

"I felt sorry for her when she withdrew from the U.S. Open because her injuries must have been very serious. I know her well. She's been tough since childhood. She will not quit unless there is no alternative," said Xia Xiyao, Li's coach in the 1990s.

"No matter what happens, I wish her well and happy," Xia added.

Li has become an icon for Chinese sports since she won the 2011 French Open, becoming the first Asian national to win a Grand Slam singles title.

She reached a career-high second in the world rankings after January's Grand Slam win, but has dropped to sixth after missing a string of tournaments. In July, Li also parted with coach Carlos Rodriguez.