In 1983 he secured a position with the International Monetary Fund as the deputy to the Executive Director, Dr. Mohamed Finaish. He served as Ambassador to the U.S. from 1997 to 2000. He returned to the IMF in 2001 and stayed until June 2005. Chatah's resignation from the IMF in 2005 coincided with the assassination of former Prime Minister Rafik Hariri on 14 February 2005; he returned to Lebanon as a senior adviser to the newly elected Prime Minister Fouad Siniora in August 2005 and served in the post until July 2008. During the July 2006 war, Chatah appeared on numerous Western news outlets as a public spokesman for the Lebanese government. When asked about the government's role in disarming local armed groups, Chatah said "we are doing it dialogue and persuasion, and trying to reach a point where the state is the sole holder of weapons and the one with the only authority throughout our territory." He also served as vice-governor of the Central Bank of Lebanon.