Mansour was educated at the University of Akron and Youngstown State University. He was the Deputy Permanent Observer of Palestine to the United Nations from 1983 to 2004. In 2005, President of the Palestinian National Authority Mahmoud Abbas appointed him to succeed Nasser al-Qudwa as Permanent Observer for Palestine to the UN.
- New Permanent Observer of Palestine Presents Appointment Letter. United Nations Press Release, 5 October 2005
- Since Palestine is not a member state of the United Nations, its representative there is a "Permanent Observer" rather than a "Permanent Representative".
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