The Biden White House is reportedly trying to rein in the U.S. ambassador to Japan, Rahm Emanuel, whose social media trolling of the Chinese government in recent weeks has become increasingly combative.

According to NBC News, Biden aides have asked Emanuel to stop mocking Xi Jinping online over China’s economic woes and the removal of several high-profile officials. As one anonymous White House official drily put it, the tweets were “not in keeping with the message coming out of this building.”

Emanuel’s sarcastic criticism of the Chinese government and Xi has predictably irritated Beijing, and that has been undermining the administration’s efforts to stabilize the deteriorating U.S.-Chinese relationship. As one administration official said, “It just fights what we are doing there in the region.” A former administration official quoted in the report was blunter: “They’re trying to calm things down and to have the ambassador to Japan attack the Chinese? It’s stupid.”

Emanuel was always a curious choice for a prominent diplomatic post, given his record as a crude, knife-fighting political operative, but in recent weeks he outdid himself with his trolling comments about China. When the then-defense minister, Li Shangfu, had not been seen in public for several weeks, Emanuel tweeted a mocking reference to Agatha Christie’s “And Then There Were None” as he called attention to the growing list of top Chinese officials removed from their positions over the last few months.