Rahm Emanuel, former mayor of Chicago, speaks in Washington, December 10, 2019.

President Joe Biden's aides have asked that Rahm Emanuel, the U.S. ambassador to Japan, stop posting messages on social media taunting Chinese President Xi Jinping, according to three administration officials.

Officials at the National Security Council told Emanuel's staff in recent days that his comments risk undermining the administration's efforts to mend deeply strained relations with China, including with a possible meeting this fall between Biden and Xi, according to the officials.