Studied theology in Naumburg and Berlin from 1971 to 1978. After Vicariate and Evangelical Parish in Vipperow / Müritz, from 1988 to 1990 he was head of the Ecumenical Meeting and Education Center in Niederndodeleben near Magdeburg. He had been performing oppositional political work in the GDR since the 1970s. In 1989 he founded the Social Democratic Party (SDP) in the GDR with Martin Gutzeit, was its representative at the Central Round Table and became its Foreign Minister in 1990 after the first free elections in the GDR. From 1990 to 2009 he was a member of the German Bundestag for the SPD. He holds numerous honorary positions in foundations and organisations, including co-chair of the foundation board of the foundation for German-Polish cooperation and chairman of the foundation board of the foundation to process the SED dictatorship. From 2013 to 2016 he was president of the Volksbund Deutsche Wargräberfürsorge e.V.