The Justice Department has decided to appoint a special counsel to investigate possible coordination between Trump associates and Russian officials seeking to meddle in last year’s election, according to Deputy Attorney General Rod Rosenstein.

Robert Mueller, a former prosecutor who served as the FBI director from 2001 to 2013, has agreed to serve in the role, Rosenstein said. The move marks a concession by the Trump administration to Democratic demands for the investigation to be run independently of the Justice Department. Calls for a special counsel have increased since Trump fired FBI Director James B. Comey last week.