<P> The 1962 United States elections were under way, and the White House had for months denied charges that it was ignoring dangerous Soviet missiles 90 miles (140 km) from Florida . The missile preparations were confirmed when an Air Force U-2 spy plane produced clear photographic evidence of medium - range (SS - 4) and intermediate - range (R - 14) ballistic missile facilities . The U.S. established a naval blockade on October 22 to prevent further missiles from reaching Cuba; Oval Office tapes during the crisis revealed that Kennedy had also put the blockade in place as an attempt to provoke Soviet - backed forces in Berlin as well . It announced that they would not permit offensive weapons to be delivered to Cuba and demanded that the weapons already in Cuba be dismantled and returned to the Soviet Union . </P> <P> After a long period of tense negotiations, an agreement was reached between U.S. President John F. Kennedy and Khrushchev . Publicly, the Soviets would dismantle their offensive weapons in Cuba and return them to the Soviet Union, subject to United Nations verification, in exchange for a U.S. public declaration and agreement to avoid invading Cuba again . Secretly, the United States also agreed that it would dismantle all U.S. - built Jupiter MRBMs, which had been deployed in Turkey against the Soviet Union; there has been debate on whether or not Italy was included in the agreement as well . </P> <P> When all offensive missiles and Ilyushin Il - 28 light bombers had been withdrawn from Cuba, the blockade was formally ended on November 21, 1962 . The negotiations between the United States and the Soviet Union pointed out the necessity of a quick, clear, and direct communication line between Washington and Moscow . As a result, the Moscow--Washington hotline was established . A series of agreements reduced U.S.--Soviet tensions for several years until the United States and Russia began to build their nuclear arsenal even further . </P> <P> The U.S. was concerned about an expansion of communism, and a Latin American country openly allying with the Soviet Union was regarded by the U.S. as unacceptable since the end of World War II, and the start of the Cold War . Such an involvement would also directly defy the Monroe Doctrine, a U.S. policy limiting U.S. involvement in European colonies and European affairs but holding that the Western Hemisphere was in the U.S. sphere of influence . </P>

What caused the end of the cuban missile crisis
find me the text answering this question