On 24th October, 1963, Ben Bradlee of Newsweek arranged for Daniel to meet President John F. Kennedy. Bradlee knew that Daniel was just about to visit Cuba in order to interview Fidel Castro. In an article in the New Republic, Daniel claims that Kennedy asked him to pass on a message to Castro: "I believe that there is no country in the world, including the African regions, including any and all the countries under colonial domination, where economic colonization, humiliation and exploitation were worse than in Cuba, in part owing to my countrys policies during the Batista regime. I believe that we created, built and manufactured the Castro movement out of whole cloth and without realizing it. I believe that the accumulation of these mistakes has jeopardized all of Latin America. The great aim of the Alliance for Progress is to reverse this unfortunate policy. This is one of the most, if not the most, important problems in America foreign policy. I can assure you that I have understood the Cubans. I approved the proclamation which Fidel Castro made in the Sierra Maestra, when he justifiably called for justice and especially yearned to rid Cuba of corruption. I will go even further: to some extent it is as though Batista was the incarnation of a number of sins on the part of the United States. Now we shall have to pay for those sins. In the matter of the Batista regime, I am in agreement with the first Cuban revolutionaries.
John F. Kennedy went onto to tell Daniel: "We cant let Communist subversion win in the other Latin American countries. Two dikes are needed to contain Soviet expansion: the blockade on the one hand, a tremendous effort toward progress on the other. This is the problem in a nutshell. Both battles are equally difficult... The continuation of the blockade depends on the continuation of subversive activities.
Daniel later wrote: "I did not really wish to suggest anything, since I had never been to Cuba and, on the other hand, I had heard from all sides tales of the privations the Cuban people were suffering owing to their isolated economic situation. But I could see plainly that John Kennedy had doubts, and was seeking a way out."
Daniel met Fidel Castro on 19th November, 1963. Daniel later described Castro as listening with "devouring and passionate interest". He made Daniel repeat three times Kennedy's indictment of Fulgencio Batista. Castro told Daniel that Kennedy could become "the greatest president of the United States, the leader who may at last understand that there can be coexistence between capitalists and socialists, even in the Americas."
Daniel was with Castro when news arrived that John F. Kennedy had been assassinated Castro turned to Daniel and said:"This is an end to your mission of peace. Everything is changed." Later Castro commented: "Now they will have to find the assassin quickly, but very quickly, otherwise, you watch and see, I know them, they will try to put the blame on us for this thing."
Castro went on to discuss the use of assassination as a political weapon. In the late 1950s e had rejected the idea of assassinating Fulgencio Batista. "I have always been violently opposed to such methods. First of all from the viewpoint of political self-interest, because so far as Cuba is concerned, if Batista had been killed he would have been replaced by some military figure who would have tried to make the revolutionists pay for the martyrdom of the dictator. But I was also opposed to it on personal grounds; assassination is repellent to me."
In 1964 Daniel left L’ Express with several other journalists, including André Gorz, to establish Le Nouvel Observateur, a weekly news magazine. In 1982 he helped establish the Saint-Simon Foundation think-tank.