Growing hostilities between the United States and its wartime ally, the Soviet Union was what formed the foundation for the cold war. This cold war lasted nearly for four decades. The growing hostilities between the US and Soviet Union, both of which were members of the Security Council and had veto powers in the UN, hampered the progress of the genocide convention. Voting in the UN General Assembly were dependent on cold war alliances and thus, coming to a decision was almost impossible.
