In this message, Khrushchev thanks Kennedy for a telegram he had written two days before congratulating the Soviet Union on "the impressive scientific achievement represented by the launching of your space vehicle to Venus."

Message from President John F Kennedy to Chairman Nikita Khrushchev. 13 Feb. 1961. Source: "Kennedy-Khrushchev Exchanges." Online archives of the US Department of State.

Khrushchev also says that he agrees with Kennedy's wish, stated in Kennedy's first State of the Union Address, for the United States and the USSR to unite their efforts in the exploration of space.

Received your telegram of congratulations on the occasion of the launching of the Soviet cosmic spaceship to the planet Venus. I express gratitude to you for this telegram giving high appraisal to this outstanding achievement of peaceful science and for wishes for success in the new stage of the exploration of the cosmos. In your speech of inauguration to the office of President, and likewise in the message to Congress of January 30 you, Mr. President, said that you would like for the Soviet Union and the United States of America to unite their efforts in such areas as the struggle against disease, mastering the cosmos, development of culture and trade. Such an approach to these problems impresses us and we welcome these utterances of yours.

Message from Chairman Nikita Khrushchev to President John F Kennedy. 15 Feb. 1961. Source: "Kennedy-Khrushchev Exchanges." Online archives of the US Department of State.