In a speech at Georgetown University on Thursday, Mark Zuckerberg laid out Facebook’s approach to moderation in terms of an ongoing commitment to free expression — and in one particular section, drew a sharp contrast with Chinese companies that may not share those values.

As Zuckerberg described it, regulators and technologists face the question of “which nation’s values are going to determine what speech is going to be allowed for decades to come,” China or the US. As he laid out Facebook’s commitment to free expression, he also emphasized that those values were already coming under threat from China.

“If another nation’s platform sets the rules,” Zuckerberg said, “our nation’s discourse could be defined by a completely different set of values.”

A full transcript of the speech is available here.

Concerns about Chinese censorship have come to a head amid the ongoing pro-democracy protests in Hong Kong. A number of US companies have attempted to stifle internal shows of support for those protests in deference to Chinese partners, including the NBA and Blizzard, which banned a professional Hearthstone player for comments made in a post-game interview.

Democrats have stepped up criticism of Facebook in recent months, most notably from Democratic front-runner Elizabeth Warren. In response, Zuckerberg has made a number of apparent overtures to conservative leaders, including private dinners with right-wing pundits like Tucker Carlson and Hugh Hewitt.

But while the partisan landscape has grown more fraught for Facebook, Zuckerberg presented the rise of Chinese internet companies as a broader national threat to American free expression:

A decade ago, almost all of the major internet platforms were American. Today, six of the top ten are Chinese. We’re beginning to see this in social media too. While our services like WhatsApp are used by protestors and activists everywhere due to strong encryption and privacy protections, on TikTok, the Chinese app, mentions of these same protests are censored, even here in the US. Is that the internet that we want?

Zuckerberg was likely referring to guidelines presented by TikTok’s parent company ByteDance, which were obtained by The Guardian last week. As written, the guidelines effectively ban criticism of the Chinese government, and forbid “demonisation or distortion of local or other countries’ history such as May 1998 riots of Indonesia, Cambodian genocide, Tiananmen Square incidents.”

Reached for comment, TikTok said that the guidelines published by The Guardian were outdated, and emphasized that US moderation decisions are made by a US-based team and are not influenced by foreign government.

“The Chinese government does not request that TikTok censor content, and would not have jurisdiction regardless, as TikTok does not operate there,” a TikTok representative said. “To be clear: We do not remove videos based on the presence of Hong Kong protest content.”

The specter of a Chinese competitor to Facebook has been raised in the past to disarm regulators, most recently when seeking support for the proposed Libra cryptocurrency. But Zuckerberg’s comments are likely to heighten the conflict between Facebook and its Chinese competitors, and put the ongoing conflict at the center of future debates over moderation policy.

“Are we going to continue fighting to give more people a voice to be heard,” Zuckerberg said at Georgetown today, “or are we going to pull back from free expression?”

3:08PM ET: Updated with statement from TikTok.