National Security Council (NSC) members favored an unannounced air assault on the missile sites, but for some of them this conjured up an image of "Pearl Harbor in reverse". There was also some concern from the international community (asked in confidence), that the assault plan was an overreaction in light of the fact that Eisenhower had placed PGM-19 Jupiter missiles in Italy and Turkey in 1958. It also could not be assured that the assault would be 100% effective. In concurrence with a majority-vote of the NSC, Kennedy decided on a naval quarantine. On October 22, he dispatched a message to Khrushchev and announced the decision on TV. The U.S. Navy would stop and inspect all Soviet ships arriving off Cuba, beginning October 24. The Organization of American States gave unanimous support to the removal of the missiles. Kennedy exchanged two sets of letters with Khrushchev, to no avail. United Nations (UN) Secretary General U Thant requested both parties to reverse their decisions and enter a cooling-off period. Khrushchev agreed, but Kennedy did not. One Soviet-flagged ship was stopped and boarded. On October 28, Khrushchev agreed to dismantle the missile sites, subject to UN inspections. The U.S. publicly promised never to invade Cuba and privately agreed to remove its Jupiter missiles from Italy and Turkey, which were by then obsolete and had been supplanted by submarines equipped with UGM-27 Polaris missiles. This crisis brought the world closer to nuclear war than at any point before or after. It is considered that "the humanity" of both Khrushchev and Kennedy prevailed. The crisis improved the image of American willpower and the president's credibility. Kennedy's approval rating increased from 66% to 77% immediately thereafter. Latin America and communism Believing that "those who make peaceful revolution impossible, will make violent revolution inevitable," Kennedy sought to contain the perceived threat of communism in Latin America by establishing the Alliance for Progress, which sent aid to some countries and sought greater human rights standards in the region. He worked closely with Puerto Rican Governor Luis Muñoz Marín for the development of the Alliance of Progress and began working to further Puerto Rico's autonomy. The Eisenhower administration, through the CIA, had begun formulating plans to assassinate Castro in Cuba and Rafael Trujillo in the Dominican Republic. When Kennedy took office, he privately instructed the CIA that any plan must include plausible deniability by the U.S. His public