(FILES) In this file photo taken on January 17, 2011 a Secret Service agent guards his post on the roof of the White House as a lamp post is adorned with Chinese and US national flags in Washington, DC. - The United States secretly expelled two Chinese embassy officials in September after they drove onto a sensitive military base in Virginia, The New York Times reported on December 15, 2019.The newspaper, which cited people with knowledge of the episode, said it appeared to be the first time in more than 30 years that the US has expelled Chinese diplomats on suspicion of espionage. (Photo by Jewel SAMAD / AFP)