President Xi Jinping warned against meddling in China’s dealings with Taiwan during a phone call with his U.S. counterpart, Joe Biden, that gave no indication of progress on trade, technology or other irritants, including Beijing’s opposition to a top American lawmaker’s possible visit to the island that the mainland claims as its own territory.

Xi also warned against splitting the world’s two biggest economies, according to a Chinese government summary of Thursday’s unusually lengthy, three-hour call. Businesspeople and economists warn such a change, brought on by Chinese industrial policy and U.S. curbs on technology exports, might hurt the global economy by slowing innovation and increasing costs.

Meanwhile, Xi and Biden are looking at the possibility of meeting in person, according to a U.S. official who declined to be identified further. Xi has been invited to Indonesia in November for a meeting of the Group of 20 major economies, making it a potential location for a face-to-face meeting.

The Chinese government gave no indication Xi and Biden discussed possible plans by U.S. House Speaker Nancy Pelosi to visit Taiwan, which the ruling Communist Party says has no right to conduct foreign relations. But Xi rejected “interference by external forces” that might encourage Taiwan to try to make its decades-old de facto independence permanent.

The tough language from Xi, who usually tries to appear to be above political disputes and makes blandly positive public comments, suggested Chinese leaders might believe Washington didn’t understand the seriousness of previous warnings about Taiwan.

“Resolutely safeguarding China’s national sovereignty and territorial integrity is the firm will of the more than 1.4 billion Chinese people,” foreign ministry spokesperson Zhao Lijian said Friday. “Those who play with fire will perish by it.”

Taiwan and China split in 1949 following a civil war that ended with a communist victory on the mainland. They have no official relations but are linked by billions of dollars of trade and investment. Both sides say they are one country but disagree over which government is entitled to national leadership.

A Ministry of Defense spokesperson said ahead of Thursday’s call that Washington “must not arrange for Pelosi to visit Taiwan.” He said the ruling party’s military wing, the People’s Liberation Army, would take “strong measures to thwart any external interference.”

Xi called on the United States to “honor the one-China principle,” according to Zhao, referring to Beijing’s position that the mainland and Taiwan are one country. The United States, by contrast, has a “one-China policy” that says Washington takes no position on the question but wants to see it resolved peacefully.

“China’s opposition to interactions between the United States and Taiwan is clear and consistent,” Zhao said.

A foreign ministry summary of the conversation cited Biden as saying the United States doesn’t support independence for Taiwan.

Coverage of the conversation in China’s entirely state-controlled media on Friday was limited to repeating government statements.

Pelosi has yet to confirm whether she will go to Taiwan, but if she does, the Democrat from California would be the highest-ranking elected American official to visit since then-Speaker Newt Gingrich in 1997.