WTA boss threatens to pull out of China

The head of the Women's Tennis Association said he is prepared to cut lucrative business ties with China if tennis star Peng Shuai remains unaccounted for and her sexual assault allegations against a top Communist Party official are not investigated.

WTA boss Steve Simon's comments on Thursday came after Tennis great Serena Williams called for an investigation into Peng's whereabouts.

Peng, a former Wimbledon and French Open doubles champion, alleged on Chinese social media earlier this month that former vice-premier Zhang Gaoli -- who is in his seventies -- had "forced" her into sex and they had an on-off relationship.

The claims, which brought the #MeToo movement into the highest echelons of China's ruling Communist Party for the first time, were quickly scrubbed from the Twitter-like Weibo platform and the 35-year-old has not been seen since.

Simon told CNN that he is willing to lose hundreds of millions of dollars worth of Chinese business in one of the WTA's biggest markets to ensure Peng's safety.

"We're definitely willing to pull our business and deal with all the complications that come with it," Simon said.

"Women need to be respected and not censored," he added.

Serena Williams on Thursday joined Naomi Osaka and Novak Djokovic in drawing attention to the case.

"I am devastated and shocked to hear about the news of my peer, Peng Shuai," former world number one Williams wrote on Twitter.

"I hope she is safe and found as soon as possible. This must be investigated and we must not stay silent."

Williams' tweet was accompanied by a photo of a smiling Peng captioned with #WhereIsPengShuai.

The WTA, the top world body for women's tennis, has called for proof that she is safe as pressure mounts on Chinese authorities to clarify Peng's status and safety.

Beijing has repeatedly refused to comment on her fate or the case.

But the editor of the state-run Global Times, Hu Xijin, tweeted Friday that he didn't believe that "Peng Shuai has received retaliation and repression speculated by foreign media for the thing people talked about".

Earlier this week, state-run CGTN published a screenshot on Twitter of what it said was an email written by Peng to Simon and other WTA officials.

In the email, Peng claims that her earlier accusations are "not true" and says she is "resting at home and everything is fine".

But doubts were quickly flagged about the awkward language used in the purported email from Peng, which Twitter users noted had a cursor visible in the screenshot posted by CGTN.

Simon said that he was struggling to believe the email was authentic.

"Whether she was coerced into writing it, someone wrote it for her, we don't know," Simon told CNN.

"But at this point, I don't think there's any validity in it and we won't be comfortable until we have a chance to speak with her."

Beijing has in the past faced allegations of using forced confessions on state media, with British regulators revoking CGTN's licence for failing to comply with fairness and privacy rules.