 He acted as papal legate to the inauguration of the Vatican pavilion at the New York World's Fair on 20 February 1964, presiding over the unveiling of the "Pietà" and presenting Cardinal Francis Spellman with a topaz brooch once worn by Pius XII as a gift from Pope Paul.Marella received four honorary doctorates on this visit to the United States, including one from the Catholic University of America, which had prohibited four liberal theologians from delivering lectures there the previous year, for which Marella commended the university.He became President of the Secretariat for Non-Christians on 19 May 1964, and again served as a papal legate, to the eighth centennial celebration of the erection of Notre-Dame Cathedral in Paris (27 May 1964), to the centennial celebration for the arrival of the first Catholic missionaries in Japan in Tokyo (12 January 1965), and to the National Congress of the Confederation of the Christian Doctrine in Pittsburgh (28 August 1966).