 In January 1957, the U.S. National Security Council began consideration of this proposal upon President Eisenhower's instruction, and then agreed to this.However, paragraph 13(d) of the Korean Armistice Agreement mandated that both sides should not introduce new types of weapons into South Korea, so preventing the introduction of nuclear weapons and missiles.The U.S. decided to unilaterally abrogate paragraph 13(d), breaking the Armistice Agreement, despite concerns by United Nations allies.