NASA has said the ISS will remain operational until 2024, but Russia -- which since the termination of the US shuttle programme is the only country able to ferry astronauts to the international station -- has said it wants to stop financing it in 2020.
Russia has delayed a ruling on its future use of the International Space Station, a source in Russia's space agency said Tuesday, as economic turmoil buffets the country's space programme.
"No decision will be made on the ISS" until the government has come up with a new long-term space space programme expected later this year, the space agency source told AFP on condition of anonymity.
Russia was supposed to have taken a decision in December about the future of the ageing international space laboratory, which was put into orbit in 1998.
Amid heightened tensions and degraded relations over the conflict in Ukraine, space exploration is the only area where US and Russia are still actively working together.
Russia's Roscosmos space agency has been forced to revise its space programme for 2016-2025 in response to the plunging ruble.
"Russia has to decide whether it will continue to participate in the ISS, whether it is building its own station, or developing a lunar programme," said Igor Marinin, editor of Space News magazine.
Daily paper Kommersant said the Russian decision on the ISS had been postponed until this spring because of uncertainty over Roscosmos's budget that has resulted from the fluctuating value of the ruble, the economic crisis sparked by Western sanctions and falling oil prices.
In January last year, NASA said the ISS, which was built at a cost of $100 billion, would have its working life prolonged by at least four years, to 2024.
But the ISS "cannot be functional without Russia," Marinin said.
In May this year, Deputy Prime Minister Dmitry Rogozin, known for his anti-Western rhetoric, said that Russia only plans to use the ISS until 2020, after which time the nation may opt to "use those resources on other promising space projects."
Sixteen countries are involved in the ISS, with Russia and the US providing most of the financial backing. The European Space Agency has yet to commit itself on financing the ISS beyond 2020.