It's Not the Clockwork.

The original proposals for Dumbarton Oaks, Washington D.C., as put forward privately by U.S. President Franklin D. Roosevelt to the British and Russians last June, called for unanimity by great powers whenever sanctions were to be applied against aggression. This veto against the use of force to be enjoyed by any one of the great powers flows in the sphere of theory from the concept of sovereignty, a sovereign power cannot be forced into war without its consent. More practically, in the sphere of politics, this veto reflected past experience with the Senate in the League and World Court fights. No proposal which would commit this country to military action without its consent stands a ghost of a chance in the Senate. Even before the meetings at Dumbarton Oaks, this principle of unanimity was accepted by British, Russians, and Chinese.