First Human in Space

Officially, the U.S. congratulated the Soviet Union on its accomplishments.

Writing for the New York Times shortly after the flight, however, journalist Arthur Krock described mixed feelings in the United States due to fears of the spaceflight's potential military implications for the Cold War, and the Detroit Free Press wrote that "the people of Washington, London, Paris and all points between might have been dancing in the streets" if it were not for "doubts and suspicions" about Soviet intentions. Other US writers reported worries that the spaceflight had won a propaganda victory on behalf of Communism. President John F. Kennedy was quoted as saying that it would be "some time" before the US could match the Soviet launch vehicle technology, and that "the news will be worse before it's better." Kennedy also sent congratulations to the Soviet Union for their "outstanding technical achievement." Opinion pages of many US newspapers urged renewed efforts to overtake the Soviet scientific accomplishments.

Adlai Stevenson, then the US ambassador to the United Nations, was quoted as saying, "Now that the Soviet scientists have put a man into space and brought him back alive, I hope they will also help to bring the United Nations back alive," and on a more serious note urged international agreements covering the use of space (which did not occur until the Outer Space Treaty of 1967).

http://en.wikipedia.org/wiki/Vostok_1