COLORADO SPRINGS, Colo. (Reuters) - Russia is open to extending its partnership in the International Space Station with the United States, Europe, Japan and Canada beyond the currently planned end of the program in 2024, the head of the Russian space agency said on Tuesday.

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“We are ready to discuss it,” Igor Komarov, general director of the Russian space agency Roscosmos, told reporters at the U.S. Space Symposium in Colorado Springs, when asked if his country would consider a four-year extension.

The $100 billion science and engineering laboratory, orbiting 250 miles (400 km) above Earth, has been permanently staffed by rotating crews of astronauts and cosmonauts since November 2000.

The U.S. space agency, NASA, spends about $3 billion a year on the space station program, a level of funding that is endorsed by the Trump administration and Congress.

A U.S. House of Representatives committee that oversees NASA has begun looking at whether to extend the program beyond 2024, or use the money to speed up planned human space initiatives to the moon and Mars.

Komarov said many medical and technological issues remain to be resolved before humans travel beyond the station’s orbit.

“I think that we need to prolong our cooperation in low-Earth orbit because we haven’t resolved all the issues and problems that we face now,” Komarov said.

The U.S.-Russian human space partnership has long endured despite the swirl of political tensions between the two countries. In 1975, for example, at the height of the Cold War, an American Apollo and Russian Soyuz capsule docked together in orbit.

“We appreciate that ... political problems do not touch this sphere,” Komarov said.

Moscow has an alternative if relations with the United States sour. Russia last year unveiled a plan to detach some of its modules and use them to create a new, independent outpost in orbit.

“We adjusted and made some minor changes in our programs ... but it doesn’t mean that we don’t want to continue our cooperation,” Komarov said. “We just want to be on the safe side and make sure we can continue our research.”

The United States is dependent on Russia’s propellant module to keep the station in orbit.