The game of “what-if” is a popular one when it comes to historical events. Shows such as “The Man in the High Castle” speculate on what would have happened if the Axis Powers had won World War II, but historians also study more realistic possibilities. When it comes to the Space Race, culminating with the July 20, 1969 moon landing, alternative histories abound, including President Richard Nixon’s never-delivered speech on the occasion of mission failure.

Another speech, actually given, by President John F. Kennedy offers another opportunity to ask “What if?” Weeks before he died in 1963, Kennedy spoke before the United Nations, suggesting NASA cooperate with the Soviets on the goal of landing on the moon. While some believe Kennedy’s prevaricating on space exploration, and who should do it, was indicative of how much he saw space dominance as a key part of winning the Cold War, many have still wondered—had he lived, would Russians and Americans have walked on the moon together?

When it came to the space program, Kennedy had not initially been keen. He’d run for president advocating against spending money on space exploration, and in his first month in office, January of 1961, he’d argued in the State of the Union address that space might be a better place for cooperation than competition, stating “Today this country is ahead in the science and technology of space, while the Soviet Union is ahead in the capacity to lift large vehicles into orbit. Both nations would help themselves as well as other nations by removing these endeavors from the bitter and wasteful competition of the Cold War. The United States would be willing to join with the Soviet Union … to increase the exchanges of scientists and their knowledge.”

Yet three months later, Kennedy was in trouble. Soviet leader Nikita Khrushchev was supporting Fidel Castro’s nascent communist government of Cuba, disturbingly close to American shores. The Bay of Pigs invasion to topple Castro, backed by Kennedy, had just ended in disaster and defeat. It was a humiliating foreign policy failure. Kennedy needed something to regain his stature on the world stage, and upstage Khrushchev.

Fortunately, or perhaps coincidentally, the era of human spaceflight had just begun.

On April 12, 1961, the Soviet Union launched Yuri Gagarin, the first person in space, into orbit around the Earth. America was three weeks away from sending its first astronaut, Alan Shepard, into space, on a much smaller rocket. For the Soviets, the victory was clear. At a celebration for Gagarin, writes William Taubman in Khrushchev: The Man and His Era , the Soviet leader boasted that “once-illiterate Russia” was now a powerful player in the race to conquer the next great frontier.

Kennedy saw an opportunity to turn a setback into a challenge with the space race. “If somebody could just tell me how to catch up,” he reportedly said to his team , “Nothing is more important.” He asked his advisers how it could be done, and they told him that with the Soviets already ahead, any goal had to be incredibly ambitious and audacious. Only then could both countries be considered to be starting from the same point. Kennedy understood, and agreed.

In a joint session of Congress on May 25, 1961, Kennedy delivered a speech that surprised many who remembered his words from earlier in the year. "I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to Earth,” he declared, before asking for an additional $7 to $9 billion to fund the program . He made no mention of racing the Soviets, but the implication was obvious. It did not mean, however, that Kennedy did not continue to talk both of cooperation and competition for the rest of his presidency.

In June of 1961, only ten days after his remarks before Congress, Kennedy and Khrushchev met for the first—and only—time in Vienna. Kennedy did not press home his point of racing to the moon. Instead, he invited the Soviet leader to join America in a cooperative lunar venture. Khrushchev turned him down, dismissing Kennedy as a lightweight, unprepared politician, a fact Kennedy himself seemed to acknowledge —“Worst thing in my life. He savaged me,” the president apparently said after the meeting. Khrushchev, in his memoirs , remembered that at their last meeting during the days-long summit, “Kennedy was very gloomy. He was not preoccupied but actually glum. When I looked at the expression on his face, I sympathized with him and felt sorry for him.”

Kennedy’s ever-changing use of the space program for potential political gain also matched Khrushchev’s. In the NASA publication “The Partnership: A History of the Apollo-Soyuz Test Project,” the Soviet leader’s style at the time was summarized thusly: “There appeared to be two Khrushchevs: one, a ‘coexistentialist’ eager for enhanced intercourse between the U.S. and the U.S.S.R.; dropping hints … about the necessity for a virtual alliance of the two powers; the other, a militant Communist and bully ready to cash in on each and every weakness and hesitation of the West.”

Kennedy may have simply been matching his opponent’s approach. It was an ever-changing, delicate balancing game for both leaders. Each championed themselves as forward-looking, while defusing aggressive actions that could lead to war.

In early 1962, Khrushchev congratulated Kennedy on America’s first mission to place a human (astronaut John Glenn in this case) in orbit. “If our countries pooled their efforts—scientific, technical, and material—to master the universe,” he said , “this would be very beneficial for the advance of science and would be joyfully acclaimed by all peoples who would like to see scientific achievements benefit man and not be used for ‘Cold War’ purposes and the arms race.”

Kennedy responded positively , but the list of possible collaborations was limited to weather satellites, spacecraft tracking and science experiments. Human space missions were mentioned only as a vague, possible future item. Sharing more rocket technology, after all, meant sharing military secrets. But as productive conversations and agreements on what was possible were made between officials of both nations, the possibilities widened.

In late September of 1963, Kennedy met with Jim Webb, the head of NASA . The president previewed the remarks he would make at the United Nations about greater cooperation with the Soviets in space and inquired if Webb would be able to turn NASA in this new direction if needed. Kennedy had been advised that, if such a plan was followed, the ambitious end-of-the-decade lunar landing deadline could be eased. In fact, Kennedy thought, he could argue that it was the breakneck competition itself that had enticed the Soviets to cooperate. Webb told the president that it was possible, though according to historian Robert Dallek, “Webb bristled at Kennedy’s policy directives, interrupting and speaking over the president” and encouraging him to consider moon landing as just a small part of space exploration. Two days later, Kennedy made his speech, describing “a joint expedition to the moon.”

It did not go as Kennedy had hoped. The Soviet press ignored the story, and Soviet officials did not comment. Public reaction in America was sharply divided; the idea seemed dead in the water.

Shortly after Kennedy’s assassination, Congress passed an appropriations bill stating that no money would be given to any international moon program. President Lyndon Johnson, newly in office, assertively championed the space race for the rest of the decade, and by the time he left office in 1969, an American moon landing that year was a virtual certainty.

The question many ponder is: Would Kennedy have pushed harder for a cooperative moon program had he not been killed? The evidence suggests he would have only if it had been politically expedient. At the time of his assassination, the concept was divisive and generally unpopular. Serious talks on cooperation only began after the Apollo 11 mission, when a race no longer mattered, culminating in crewed American and Soviet spacecraft docking in orbit in 1975.

Today, the joint Russian and American International Space Station is a wonderful example of where such collaboration can lead, and a reminder of Kennedy’s efforts at the beginning of the Space Age to always keep the door of collaboration open, even when faced with a fearsome competitor.