Chinese media outlets have warned that Donald Trump is threatening healthy U.S.-China relations, on which “world peace and prosperity” depend, by behaving like a “diplomatic rookie” on issues like Taiwan, trade and the South China Sea.

Comment pieces published on China’s state media channels and newspapers with ties to Beijing criticized the President-elect in response to a series of tweets he issued on Sunday, chiding China for taxing U.S. imports, devaluing its currency, and building military installations in the South China Sea. This comes after he broke with decades of diplomatic niceties on Dec. 3 and took a phone-call with Taiwan’s President Tsai Ing-wen.

“Trump may dislike, distrust the diplomatic establishment in Washington D.C., and aspire to rework U.S. foreign policies” China Daily wrote in a Dec. 6 editorial. “But he should first come to terms with the real, not imagined, reality of international relations before wielding the scalpel, because a misstep as president will be far more damaging than one as president-elect.”

“To stop acting like the diplomatic rookie he is, the next U.S. president needs help in adapting to his forthcoming role change. Otherwise, he will make costly troubles for his country, and find himself trying to bluster his way through constant diplomatic conflagrations” China Daily wrote.

Even though there has been little official reaction to Trump’s tweets and talk with Tsai, China uses state media to let its policy positions be known. “The U.S. cannot (and should not) try to dictate the policy of another sovereign state,” People’s Daily warned. “Sovereignty means that China, for example, is not always going to do what the U.S. wants.”

“An irrational and hasty “get tough with China” policy would be detrimental to U.S. long-term interests … Not only is the U.S. more dependent on China than Trump seems to realize, but world peace and prosperity depend on the healthy develop of China-U.S. relations” People’s Daily wrote. “Trump needs to get the China-U.S. relationship right.”

The Global Times says China should “brace itself” for fluctuations in relations with China and U.S., warning that Trump is treating China as a lamb for the slaughter: “Trump’s China-bashing tweet is just a cover for his real intent, which is to treat China as a fat lamb and cut a piece of meat off it. Trump wants to revive US economy, but he knows that his country is not as competitive as it used to be. He is trying to pillage other countries for the prosperity of the US. Trump [seems] to be wanting to make the US a new economic empire in the 21st century under his leadership, which is about to smash current world economic order. However, he doesn’t know that the US is the biggest beneficiary from the current world order, and he wants to reshape the world order into a winner-takes-all one.”

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