As mayor, he has been a visible peace activist. He is active in the Mayors for Peace organization, serving as the president of their World Conference. The 2020 Vision Campaign launched in 2003, which aims to eliminate nuclear weapons, has earned Mayors for Peace the "World Citizenship Award" from the Nuclear Age Peace Foundation in 2004, the "Sean McBride" Award from the International Peace Bureau in 2006, and the Nuclear-Free Future Award from the Franz-Moll Foundation in 2007. He has also been an advocate of the abolition of nuclear weapons, and a vocal critic of George W. Bush. Since May 2007 he is also Councillor at the World Future Council.