Washington  - Two years after the United States made history with the first manned landing on the moon, US astronauts David Scott and James Irwin placed a plaque on the lunar surface honouring their American brothers and Soviet counterparts who died in pursuit of space exploration.

The 1971 gesture to the 14 astronauts and cosmonauts came as the United States and the Soviet Union began to forge a cooperative effort after more than a decade of intense competition between the two Cold War rivals for superiority in space.

July 20 will mark the 40th anniversary of the Apollo 11's landing on the moon, followed by Neil Armstrong's stroll on the surface and uttering of his famous words: "That's one small step for (a) man, one giant leap for mankind."

The lunar landing captured the public's imagination eight years after president John F Kennedy set the goal of putting a man on the moon by the end of the 1960s, but it also boosted American prestige in the world after years of embarassingly trailing Soviet advances in space.

Americans watched in horror as the Soviets successfully orbited the first artificial satellite - Sputnik - in 1957. And Kennedy's declaration came weeks after cosmonaut Yuri Gagarin became the first man in space.

"Space was a way of demonstrating national power and advancing national prestige and the reputation of power in a very visual and impressive, but non-threatening way," John Pike, an analyst at Globalsecurity. org, said.

"The early Soviet space triumphs had created the impression that they were going to win, and that the Soviets were superior and that (the United States was) going to wind up on the dust heap of history," he said.

The US triumph on the moon left the United States in a dominant position in space, even as the two sides differed over who was the winner of the race. The Soviets laid claim to the title by citing Sputnik and Gagarin, while the United States insisted that landing on the moon had made it the winner.

But there was little doubt the moon landing for the most part ended the space rivalry while the Cold War was still at its peak. The Soviets concluded it was not worth the time and resources to finish second in the drive to get to the moon, and devoted their efforts elsewhere, going on to build the first manned space station.

The United States focused on becoming the first to develop a space shuttle, a vehicle that could land back on Earth like a plane. The successful programme is still flying, despite the 1986 and 2003 Discovery and Columbia disasters.

Meanwhile, the two countries also began exploring ways to work together on space - agreements that not only advanced science but also contributed to easing Cold War tension. That spirit was most symbolized by the docking of the Soviet Soyuz and American Apollo spacecrafts in 1975 and culminated in the creation of today's International Space Station.

Jack Matlock, a former ambassador to the Soviet Union and Cold War historian, said cooperation in space was essential for limiting its use to peaceful purposes and keeping it safe for communications and other satellites.

"The fact that we cooled it and cooperated on the peaceful use of space was extremely important," he said in an interview.

That cooperation could be tested in the coming years. Although improved since President Barack Obama's visit to Moscow earlier this month, relations between the two sides have been at their lowest point since the end of the Cold War.

With the space shuttle programme scheduled to be mothballed at the end of 2010 and the next American vehicle, the Orion, not expected to be ready before 2015, the United States will be dependant on Russia for human access to space. The gap has subjected the National Space and Aeronautics Agency (NASA) to criticism that poor planning has left the United States vulnerable to the whims of the Kremlin.

"My hope is our relations with Russians are going to get better, but who knows what geopolitics will be for the next 10 years," Senator Bill Nelson, a former astronaut, said in June. (dpa)