The space partnership between the United States and Russia, which dates back to the early 1990s with an astronaut-cosmonaut exchange program, so far has remained outside the political rancor and economic ramifications stemming from Russia’s annexation of Ukraine’s Crimea peninsula earlier this year.

But the escalating tensions now threaten the future of the International Space Station, or ISS, a 15-nation research laboratory overseen by the United States and Russia. Rotating crews of NASA astronauts and Russian cosmonauts, along with members of the European, Canadian and Japanese astronaut corps, have lived together aboard the orbital outpost since November 2000.  Construction, however, was finished just three years ago.

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With science operations finally in full swing, the Obama Administration last year confirmed NASA’s plan to keep the station in orbit until at least 2024, four years longer than original projections.

Russia, however, now has other ideas.

“Roscosmos doesn’t plan to continue cooperation with the US on the ISS after 2020,” Dmitry Rogozin, a Russian deputy prime minister who oversees the country’s space and defense programs, wrote on Twitter.

“We are very concerned about continuing to develop high-tech projects with such an unreliable partner as the United States, which politicizes everything,” Rogozin added during a press conference on Tuesday.

Presumably stoking Rogozin’s ire was the United States’ decision to deny export licenses for some high-tech items.

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“We’ve repeatedly warned our colleagues at the political and professional levels … that sanctions are always a boomerang. They always come back around and are simply inappropriate in such sensitive spheres as cooperation in space exploration, production of spacecraft engines and navigation, not to mention manned space flights. Sanctions are like releasing a bull in a china shop,” Rogozin said.

A translated transcript of the news briefing was posted on the Russian government’s website.

Rogozin, who is among 11 individuals being sanctioned by the United States to punish Russia for its takeover of Crimea, also said Russia no longer will provide rocket engines for U.S. launchers that fly U.S. military payloads. That’s a direct hit at United Launch Alliance, a Boeing-Lockheed Martin partnership, which uses the Russian-made RD-180 engine in its Atlas 5 rocket, one of two rockets it sells that have a lock on flying most of the U.S. military’s spacecraft.

Rival Space Exploration Technologies, or SpaceX,  is suing to break the United Launch Alliance monopoly and raised the prospect that the sale of the RD-180 engines personally benefits Rogozin and therefore may be in violation of U.S. sanctions.

A judge in the case issued a temporary injunction on the RD-180 sales, but lifted it last week after officials with the U.S. departments of State and Treasury weighed in with letters saying they were not aware of any direct benefit to Rogozin from the engines’ sales.

The court has not yet ruled on the larger issue raised by SpaceX’s protest.

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Meanwhile NASA said that it has not received any official notification from Russia of any changes in its joint space programs.

“Space cooperation has been a hallmark of US-Russia relations, including during the height of the Cold War, and most notably, in the past 13 consecutive years of continuous human presence on board the International Space Station. Ongoing operations on the ISS continue on a normal basis,” NASA said in a statement.

“We agreed from the very start that (the ongoing International Space Station) cooperation will remain unchanged, and therefore its is immune to sanctions,” Oleg Ostapenko, head of the Russian federal space agency, said at the news conference, the transcript shows.

Added Rogozin, “Our U.S. colleagues have told us that they would like to extend the ISS’ operation deadline until 2024. But the Russian Federal Space Agency and our colleagues, including the Academy of Sciences and the Russian Foundation for Advanced Research Projects are now ready to make some new long-term strategic proposals linked with the subsequent development of the Russian space program after 2020. We plan to use the ISS exactly up to 2020.”

United Launch Alliance said it has enough RD-180 engines in inventory to meet its launch needs for the next two years.