Russia's new space chief said his country plans to withdraw from the International Space Station (ISS) after 2024, though a senior NASA official said Moscow has not communicated its intent to pull out of the two-decade-old orbital partnership with the United States.
While heightened tensions between Moscow and Washington over Russia's invasion of Ukraine for months have raised doubts about future American-Russian space cooperation, the announcement by Yuri Borisov, the newly appointed director-general of Russia's space agency Roscosmos, came as a surprise.
The two former Cold War adversaries signed a crew exchange agreement less than two weeks ago allowing US astronauts and Russian cosmonauts to share flights on each other's spacecraft to and from the ISS in the future.
The US space agency has said it plans to keep the ISS in operation through 2030.
"Of course, we will fulfil all our obligations to our partners, but the decision about withdrawing from the station after 2024 has been made," Borisov told Russian President Vladimir Putin on Tuesday.
Robyn Gatens, NASA's ISS director, said her Russian counterparts have not communicated any such intent as required by the intergovernmental agreement on the orbiting research platform.
"Nothing official yet," Gatens said in an interview at an ISS conference in Washington. "We literally just saw that as well. We haven't gotten anything official."
U.S. State Department spokesperson Ned Price also said Russia's announcement was unexpected, calling it an "unfortunate development."
Launched in 1998, the ISS has been continuously occupied since November 2000 while operated by an American-Russian-led partnership that also includes Canada, Japan and 11 European countries.
The space station was born in part from a foreign policy initiative to improve American-Russian relations following the collapse of the Soviet Union and the Cold War hostility that spurred the original US.-Soviet space race.
The ISS arrangement, which has endured numerous strains over the years, has stood as one of the last links of civil cooperation as Russia's February 24 invasion of Ukraine sent relations between Washington and Moscow to a new post-Cold War low.
NASA and Roscosmos had been in talks to extend Russia's ISS participation to 2030. The White House this year approved NASA's plans to continue running the ISS until then.
NASA officials had previously said bilateral cooperation aboard the space station remained intact.
Borisov's remarks followed a pattern similar to those of his predecessor, Dmitry Rogozin, who during his tenure would occasionally signal an intent to withdraw from the ISS - in contrast with official talks between NASA and Roscosmos.
Asked for clarification on Russia's space station plans, a Roscosmos spokeswoman referred Reuters to Borisov's remarks without saying whether it represented the agency's official position.
NASA has called Russia crucial to keeping the space station running, stressing the technical interdependence of the American and Russian segments of the ISS.
For example, while US gyroscopes provide day-to-day control over ISS orientation in space and US solar arrays augment power supplies to the Russian module, the Russian unit provides the propulsion used to keep the station in orbit.
The station, spanning the size of a football field, orbits some 400 km above Earth.
Former Russian space chief Rogozin had previously said that Russia could not agree to extend its ISS role beyond 2024 unless the United States lifts sanctions on two Russian companies blacklisted for suspected military ties.
Putin removed Rogozin as space chief on July 15, replacing him with Borisov, a former deputy prime minister and deputy defence minister.