FILE - Peng Shuai of China celebrates after winning the women's singles match against Venus Williams of the United States in the China Open tennis tournament at the National Tennis Stadium in Beijing, Monday, Oct. 3, 2016. The disappearance of tennis star Peng Shuai in China following her accusation of sexual assault against a former top Communist Party official has shined a spotlight on similar cases involving political dissidents, entertainers, business leaders and others who have run afoul of the authorities. (AP Photo/Andy Wong, File)

FILE - Peng Shuai, of China, drops to her knees in pain during the semifinals of the 2014 U.S. Open tennis tournament against Caroline Wozniacki, of Denmark, on Sept. 5, 2014, in New York. Struggling to stay upright as suffocating heat and humidity drained her energy in the U.S. Open semifinals, Peng Shuai refused to give up. She paused between points to clutch at her left thigh and put her weight on her racket as if it were a cane. Helped off the court and diagnosed with heat stroke, doctors told her to quit. But Peng still came back for more. Six more points until she eventually collapsed to the ground and Caroline Wozniacki, her opponent in that 2014 match, came around the net to check on her. Only then, with her body pushed to the absolute limit -- maybe even beyond the limit -- did Peng retire from the match that marked the pinnacle of her singles career. (AP Photo/Mike Groll)

FILE - Peng Shuai of China returns a ball during the semifinal match against Shahar Peer of Israel, unseen, in the Guangzhou WTA Tour in Guangzhou in south China's Guangdong province Saturday, Sept. 19, 2009. An email purportedly from Chinese professional tennis player Shuai that a Chinese state media outlet posted on Twitter has increased concerns about her safety as the sport's biggest stars and others abroad call for information about her well-being and whereabouts since her accusation about two weeks ago that she was sexually assaulted by a former top government official. (AP Photo, File)

China's Peng Shuai reacts while competing against Canada's Eugenie Bouchard in their first round match at the Australian Open tennis championships in Melbourne, Australia, Tuesday, Jan. 15, 2019. The disappearance of tennis star Peng Shuai in China following her accusations of sexual assault against a former top Communist Party official has shined a spotlight on similar cases involving political dissidents, entertainment figures, business leaders and others who have run afoul of the authorities. (AP Photo/Mark Schiefelbein)