He was state secretary for the research policy (1990), and later state secretary and minister for development cooperation (1991). Within the first cabinet of Jean-Luc Dehaene he was state secretary for development cooperation (1991-1995). From 1995 to 1999 he was the Belgian minister of foreign affairs. He left politics upon being appointed to the then Belgian Court of Arbitration on 10 August 2001. He retired from the Court, since 2007 reformed as the Constitutional Court, in October 2019 upon reaching the mandatory retirement age of 70.