From there, he moved to New York, where he was deputy director of the Economic Department at the Permanent Mission of Germany to the United Nations until 2004.

Berger then became Head of the German Representation Office in the Palestinian Territories before moving back to the Parliamentary and Cabinet Division in 2006, this time as Director.

As State Secretary, Berger was responsible for the two political departments as well as the coordination of German foreign policy in Europe and the Asia-Pacific region and the Crisis Commissioner.

[7] Shortly after taking office as Federal Minister for Foreign Affairs, Annalena Baerbock decided in December 2021 to dismiss Berger and reinstate his predecessor Andreas Michaelis, former German ambassador to London, as State Secretary.

[7] Berger in turn became ambassador to the United Kingdom and was received by Queen Elizabeth II on 7 July 2022, to present his credentials.