After getting into a physical altercation last fall with a Chinese official over the White House’s “nuclear football,” Chief of Staff John Kelly reportedly said that he will only accept an apology if a senior Beijing official travels to Washington and expresses contrition while standing under a U.S. flag, The Wall Street Journal reported Friday. The altercation occurred during Trump’s visit to Beijing, Axios reported, when President Trump walked into the Great Hall of the People. A Chinese official tried to stop the military aide who was carrying the nuclear football—the portable device capable of launching the U.S. arsenal and likely triggering World War III—from following him, and another official alerted Kelly. As Kelly moved to resolve the situation, a Chinese security official is said to have grabbed him. Kelly pushed off the official’s hand, and a U.S. Secret Service agent tackled the official to the ground. Axios noted that no Chinese officials ever touched the nuclear controls, and the head of the Chinese security detail later apologized to the Americans—which, apparently, wasn’t enough to satisfy Kelly.