The Women's Tennis Association (WTA) has become the world's "most effective" human rights organization over its leadership on the Peng Shuai case and willingness to lose money to stand by its principles, said Kelley Eckels Currie, former U.S. Ambassador-at-Large for Global Women's Issues.

The whereabouts of Peng, a former doubles world No. 1, became a matter of international concern for nearly three weeks after she posted a message on social media alleging that a former top Chinese government official had sexually assaulted her. She reappeared over the weekend in Beijing.

The WTA, the main organizational body for women's tennis internationally, has called for a transparent investigation and assurances about Peng's safety and well-being, and has threatened to pull out of tournaments in China over the matter.