Cuban Missile Crisis 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. The US announced it 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. After several days of tense negotiations, an agreement was reached between US President John F. Kennedy and Khrushchev. Publicly, the Soviets would dismantle their offensive weapons in Cuba and
Cuban Missile Crisis to endorse the missile swap but others continued to oppose the offer. Finally, Kennedy ended the debate. "We can't very well invade Cuba with all its toil and blood," Kennedy said, "when we could have gotten them out by making a deal on the same missiles on Turkey. If that's part of the record, then you don't have a very good war." Kennedy immediately responded, issuing a statement calling the letter "an important and constructive contribution to peace." He continued this with a formal letter: Kennedy's planned statement would also contain suggestions he had received from his adviser Schlesinger Jr.