The White House has ordered federal health officials to treat top-level coronavirus meetings as classified, an unusual step that has restricted information and hampered the U.S. government's response to the contagion, according to four Trump administration officials.

The officials said that dozens of classified discussions about such topics as the scope of infections, quarantines and travel restrictions have been held since mid-January in a high-security meeting room at the Department of Health & Human Services (HHS), a key player in the fight against the coronavirus.

Staffers without security clearances, including government experts, were excluded from the interagency meetings, which included video conference calls, the sources said.

"We had some very critical people who did not have security clearances who could not go," one official said. "These should not be classified meetings. It was unnecessary."

The sources said the National Security Council (NSC), which advises the president on security issues, ordered the classification."This came directly from the White House," one official said.