Born in Damascus in Syria, Sasson studied at an Alliance School in his hometown and the Université Saint-Joseph in Beirut. He became a member of the Arab National Movement, and edited a Jewish-Arab newspaper named al-Hayat. He made aliyah in 1927 and worked as an electrician, journalist and lecturer on Middle East affairs.
He began working in the political department of the Jewish Agency, serving as head of the Arab department between 1933 and 1948. A member of the Jewish delegation to the United Nations between 1947 and 1948 and at the ceasefire negotiations in 1949, he worked as director of the Middle East department of the Foreign Affairs Ministry between 1948 and 1950, before heading an office in Paris for contacts with Arab nations. He is reported by Benny Morris to have been a member in 1948 of one of the government's unofficial Transfer Committees, set up to facilitate the removal of Arabs from their towns and villages. He also served as the Israeli envoy to Turkey (1950–1952), an envoy and ambassador to Italy (1953–1960) and ambassador to Switzerland (1960–1961).