Azar will visit Taiwan in coming days in the highest-level visit by an American Cabinet official since the break in formal diplomatic relations between Washington and Taipei in 1979.
Beijing's top envoy to Washington, Mr Cui Tiankai, said on Wednesday that Beijing did not want to see a Cold War break out between China and the U.S., and that relations between the two countries are suffering unprecedented strain, something both sides should work together to remedy.
China has lodged stern representations with the United States over the upcoming visit of US Secretary of Health and Human Services Alex Azar to Taiwan, the Foreign Ministry in Beijing said on Wednesday.
China claims self-ruled Taiwan as its own and has threatened to annex it by force if necessary. "This is the highest-level visit by a U.S. Cabinet official since 1979!"
Trump broke diplomatic norms after his election victory in 2016 when he took a congratulatory call from President Tsai - the first time a US leader had spoken directly to his Taiwanese counterpart since Washington switched diplomatic recognition to Beijing.
"China firmly opposes official exchanges between the U.S. and Taiwan", Wang Wenbin, a spokesman of China's Ministry of Foreign Affairs, said at a regular briefing.
Taiwan's foreign ministry has confirmed the trip and said Azar would meet President Tsai Ing-wen.
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Tsai tweeted to Azar that "Your timely visit is another testament to the strong Taiwan-US partnership based on our longstanding friendship & shared values".
His department, describing the trip as "historic", said Azar would be accompanied by Mitchell Wolfe, chief medical officer of the U.S. Centers for Disease Control and Prevention, and other members of the administration.
In Beijing, a spokesman for the Chinese foreign ministry said Azar's visit would endanger "peace and stability" in the region. "Taiwan and the USA are like minded partners cooperating closely in combating coronavirus and promoting freedom democracy & human rights worldwide".
The last cabinet-level trip to Taiwan was in 2014 when the then head of the Environmental Protection Agency visited.
Taiwan's strong performance in handling its COVID-19 outbreak has also won it plaudits while highlighting its exclusion from the World Health Organization and other United Nations bodies.
Despite its proximity and close economic ties to China, Taiwan has fewer than 500 cases and just seven deaths thanks to a world-class tracing and testing regime and the island virtually shuttering its borders.
The tensions have sparked warnings from officials that the risk of military clash over Taiwan is rising precariously.