The move comes as part of a reorganisation within the Leo Burnett Group, which has resulted in the creation of Arc North America to subsume its US below-the-line operations: iLeo North America, Frankel and Semaphore Partners.
Brien has been the president of corporate business development at Publicis' Starcom MediaVest Group since 2001, based in Chicago.
He joined what has become the Publicis Groupe as an executive media director at Leo Burnett London in 1992 from Grey London, where he had worked for ten years.
He became the managing director in 1996 and the chief executive in 1997.
Brien's promotion was announced by the Leo Burnett chief executive, Linda Wolf, amid a raft of appointments at the network.
The Lowe New York chief executive, Tom Bernadin, has been hired as the president and chief executive of Leo Burnett's US operation. He is being groomed to take over from Wolf, who is set to retire in 12 to 18 months.