Weissglas was the Bureau Chief of the Prime Minister of Israel Mr. Ariel Sharon and a Special foreign affairs Advisor to the Prime Minister from May 2002 to June 2006. Weissglas was responsible for the Prime Minister's contact with the White House, State Department and other branches of the U.S. administration, and also with the EU Leadership and heads of the major European countries. As well, he conducted negotiations with the Palestinian Authority, Jordan and Egypt, and was involved on behalf of the State of Israel in the process of drafting the Road Map for Peace; the preparation of the Gaza Strip Disengagement plan; and other major political initiatives.