After serving as the first Jordanian Ambassador to the State of Israel after the 1994 Peace Treaty, and also as Ambassador to the United States, he had been the foreign minister from January 2002 until October 2004, when he gained the post of deputy prime minister in a cabinet reshuffle which was designed to continue the process of reform and the shrinking of the bureaucracy. He was the deputy prime minister of Jordan in Adnan Badran's cabinet from 25 October 2004 to 28 November 2005. He was at the Jordanian Senate until 16 March 2007 when he joined the World Bank as Senior Vice President for External Affairs. He has written a book called The Arab Center which was released on 9 May 2008. He is also a Middle East specialist for the Carnegie Endowment for International Peace. In 2011 Muasher took seat in the advisory council of The Hague Institute for Global Justice.