World No. 1 Novak Djokovic, former star Martina Navratilova and women's tour founder Billie Jean King have all backed the WTA in its decision to suspend tournaments in China over concerns for Peng Shuai.
Olympic chiefs, in the meantime, confirmed Thursday that they held a second video call with the Chinese tennis star.
The women's tennis tour decided what its chairman Steve Simon called enduring "serious doubts" about the safety of Chinese player Peng, who accused a former Communist Party leader of sexual assault.
Simon reiterated his calls for China to conduct "a full and transparent investigation – without censorship," into Peng's claim that former vice-premier Zhang Gaoli "forced" her into sex.
The WTA's move to suspend its tournaments in China, including Hong Kong, won the backing of some of the biggest names in tennis.
The decision could potentially cost the WTA hundreds of millions of dollars because China is one of its biggest markets.
Djokovic called the WTA's stance "very bold and very courageous," while 12-time Grand Slam singles winner King tweeted that the WTA was "on the right side of history."
Tennis great Martina Navratilova challenged the International Olympic Committee (IOC) to respond, writing on Twitter that "so far I can barely hear you!!!"
China will host the Beijing Winter Olympics in February.
The IOC, whose president Thomas Bach spoke to Peng for 30 minutes on Nov. 21 in one of the first contacts that a Western organization had with her, said it had held a second call Wednesday.
The call had confirmed that Peng "appeared to be safe and well, given the difficult situation she is in," the IOC said.
Bach faced criticism after the first call for failing to make demands about Peng's safety and the IOC defended its approach in a statement Thursday.
"We are using 'quiet diplomacy' which, given the circumstances and based on the experience of governments and other organizations, is indicated to be the most promising way to proceed effectively in such humanitarian matters," the IOC said.
But the uncertainty over Peng has reignited calls for a diplomatic boycott of the Beijing Games over China's human rights record.
"In good conscience, I don't see how I can ask our athletes to compete there when Peng Shuai is not allowed to communicate freely and has seemingly been pressured to contradict her allegation of sexual assault," Simon said.
In the meantime, the Chinese Tennis Association on Thursday expressed "indignation and firm opposition" to the WTA's announcement, state-owned newspaper Global Times reported.
And Chinese foreign ministry spokesman Wang Wenbin said the country was "firmly opposed to acts politicizing sport."
The 35-year-old Peng, a doubles champion at Wimbledon and the French Open, has been at the center of international concern for the past month.
She was not seen for weeks following her allegations on the Twitter-like Weibo platform that Zhang, now in his 70s, coerced her into sex during a years-long on-off relationship.
Her allegations, posted on Nov. 2, were quickly scrubbed from the internet in China and online discussions about them remain censored. Zhang has not responded.
The Global Times on Thursday accused the WTA in an editorial posted only on Twitter of "an exaggerated show" and "forcing (Peng) to complain in accordance with the imagination and expectations of Western public opinion."
Peng's claims against Zhang were the first time China's #MeToo movement has touched the highest echelons of the ruling Communist Party.
State media have pointed to an email attributed to Peng and photos of her at a Beijing tennis event as evidence of her safety.
Simon said he still had "serious doubts that she is free, safe, and not subject to censorship, coercion, and intimidation."
The European Union, the United Nations, the United States and Britain have all called for proof of Peng's whereabouts and well-being.
Next year's WTA schedule had not yet been announced, but China looks unlikely to be hosting major international sport – except the Olympics – any time soon because of its strict coronavirus policies.
In 2019, China hosted 10 WTA events with total prize money topping $30 million.
Speaking on CNN, Simon said he had been unable to contact Peng directly despite multiple attempts.
Asked if the WTA had been contacted by any corporate sponsors of the Olympics or other sports with big business in China, such as the NBA, Simon said: "We haven't heard from the partners involved in the Olympics and other properties involved in China.
"Our position here is very, very clear: I can only imagine the range of emotions and feelings that are likely going through Peng right now.
"We hope that she feels that none of this is her fault and that we're very proud of her."