This telegram from President Kennedy is the first one that indicates a serious pursuit of a joint space effort between the US and the USSR.

I welcome your statement that our countries should cooperate in the exploration of space. I have long held this same belief and indeed put it forward strongly in my first State of the Union message.

We of course believe also in strong support of the work of the United Nations in this field and we are cooperating directly with many other countries individually. But obviously special opportunities and responsibilities fall to our two countries.

I am instructing the appropriate officers of this Government to prepare new and concrete proposals for immediate projects of common action, and I hope that at a very early date our representatives may meet to discuss our ideas and yours in a spirit of practical cooperation.

Letter from President John F Kennedy to Chairman Nikita Khrushchev. 21 Feb. 1962. Source: "Kennedy-Khrushchev Exchanges." Online archives of the US Department of State.