Belgian riot police officers stand guard as activists of an Iranian exiled opposition group block a street in front of the EU Commission headquarters in Brussels. Belgian riot police officers (top) stand guard as activists of an Iranian exiled opposition group from several countries block a street protesting against EU negotiations with Tehran over Iran's nuclear situation in front of the European Commission headquarters in Brussels May 18, 2005. There is no certainty the U.N. Security Council would back a U.S. or European request to punish Iran if Tehran resumed work on what Washington fears is part of a nuclear weapons program, U.N. diplomats said on Monday. REUTERS/Francois Lenoir