Between 1949 and 1971, US–China relations were uniformly hostile, with frequent propaganda attacks in both directions. At the 1954 Geneva Conference, Secretary of State John Foster Dulles forbade any contact with the Chinese delegation, refusing to shake hands with Zhou Enlai, the lead Chinese negotiator. Relations deteriorated under President John F. Kennedy (1961–1963). Before the Cuban Missile Crisis, policymakers in Washington were uncertain whether or not China would break with the Soviet Union on the basis of ideology, national ambitions, and readiness for a role in guiding communist activities in many countries. New insight came with the Sino-Indian border war in November 1962 and Beijing's response to the Cuban Missile Crisis. Kennedy administration officials concluded that China was more militant and more dangerous than the Soviet Union, making better relations with Moscow desirable, with both nations trying to contain Chinese ambitions. Diplomatic recognition of China remained out of the question, as a crucial veto power on the UN Security Council was held by America's ally on Taiwan. The United States continued to work to prevent the PRC from taking China's seat in the United Nations and encouraged its allies not to deal with the PRC. The United States placed an embargo on trading with the PRC, and encouraged allies to follow it.