A longtime professor at a U.S. Air Force school in Alabama has pleaded guilty to lying to a federal investigator about his contacts with a Chinese official, prosecutors said Monday.

Xiaoming Zhang, 69, a naturalized citizen of Chinese descent, taught at Air War College on Maxwell Air Force Base in Montgomery. He faces up to five years in prison after pleading guilty to a charge of making false statements to a federal agent, according to a statement from the U.S. Justice Department.

Zhang, who held a security clearance because of his work, wasn’t accused of passing along secrets — just of concealing his face-to-face meetings and emails with a Chinese official, prosecutors said. The charge filed last month accused him of doing so from December 2012 until January 2017.

A teacher at the Air War College since 2003, Zhang became aware that the official was trying to use their relationship to make contact with other possibly valuable people, said the statement.

Zhang lied about his contacts in 2017 during a meeting with an investigator from the Office of Management and Budget, court documents show. He initially misled an FBI agent during a meeting in 2020 but later admitted the relationship and said he’d tried to conceal it because he knew it was improper.

A judge didn’t immediately schedule a sentencing hearing.