Their main inspiration was the League of Nations ; however , their goals were to rectify the League 's imperfections in order to create an organization that would be “ the primary vehicle for maintaining peace and stability . ” Roosevelt 's main role was to convince the different allies , especially Winston Churchill of the United Kingdom and Joseph Stalin of the Soviet Union , to join the new organization . The negotiations mainly took place during the Dumbarton Oaks Conference and the Yalta Conference , where the three world leaders tried to reach a consensus concerning the United Nations ' structure , purposes and principles . “ Roosevelt saw the United Nations as the crowning achievement of his political career . ” In 1945 , representatives from 50 countries met in San Francisco for the United Nations Conference on International Organization . They deliberated on proposals that had been drafted by representatives of the Republic of China , the Soviet Union , the United Kingdom and the United States at the Dumbarton Oaks Conference between August and October 1944 . Roosevelt , Churchill and Stalin reviewed the Dumbarton Oaks proposal during the Yalta Conference in February 1945 . The purpose of the conference was to discuss post-war settlements and to reach a final agreement concerning “ the UN ’s structure and membership and set the date of the San Francisco organizing conference . ” The world leaders eventually agreed on Roosevelt 's proposal to give certain members a veto power so “ that the Organization could take no important action without their joint consent . ” Though the veto power question created a lot of disagreement among the different signatories , its inclusion in the charter was never a matter of negotiation for Roosevelt and his allies . Finally , during the Yalta conference , Stalin agreed to make the USSR a member of the United Nations
Yalta Conference
Yalta Conference
United States and the United Nations