U.S. officials have rejected China’s request that Taiwan President Tsai Ing-wen be prevented from making a stopover in New York City next month, as the fallout continues from President-elect Donald Trump’s protocol-busting phone call last week.

Trump spoke with Tsai by telephone for 10 minutes on Friday, in the first direct contact between the leaders of the U.S. and Taiwan since diplomatic relations were severed in 1979.

Officials in Beijing, which claims sovereignty over self-governing Taiwan, were furious. They have now asked the U.S. to prevent Tsai from using New York City as a stopover en route to scheduled meetings in Guatemala and El Salvador early next month, according to a Foreign Ministry statement sent to Reuters.

China hopes the U.S. “does not allow her transit, and does not send any wrong signals to ‘Taiwan independence’ forces,” read the statement.

Tsai belongs to the Democratic Progressive Party, which officially backs independence for Taiwan. She has discreetly shied away from discussing the topic since her presidential campaign, but she and the DPP remain deeply distrusted in Beijing.

A State Department spokeswoman told Reuters that stopovers would continue “based on long-standing U.S. practice, consistent with the unofficial nature of our relations with Taiwan.”

Relations between Taiwan and China, which effectively split in 1949 following China’s civil war, have warmed in recent years owning to the 1992 Consensus, drawn up between Beijing and the Kuomintang (KMT) administration in Taipei at the time. The consensus states that both sides belong to “one China” even if they disagree on which is the legitimate government. Tsai, however, has refused to acknowledge the consensus, describing it as “an option, but not the only one.”

At the same time, she has been careful to be seen to be supporting the status quo. During a meeting with American reporters on Tuesday, Tsai said, “I do not foresee major policy shifts in the near future because we all see the value of stability in the region.”

Trump has meanwhile been unapologetic about his phone call with Tsai. The fear now is that the President-elect will meet Tsai personally when she passes through New York City.

The consequences of a face-to-face encounter would be “extremely serious,” says Professor Chu Shulong, an international relations expert at Beijing’s Tsinghua University. “The relationship between China and the U.S. would hit rock bottom.”

“America is a strong country but can’t do whatever it wants,” he adds. “China has a say in the U.N., and regarding many international issues, such as North Korea, Iran, climate change, etc., which could also constrain the U.S.”

— With reporting by Yang Siqi / Beijing

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