Cosmonauts on the ISS say they are no longer permitted to use US facilities
The International Space Station, once a place where astronauts would share food and facilities, is said to be embroiled in a Cold War-like stand-off.
A Russian cosmonaut has complained he is no longer allowed to use a US toilet as well as a US exercise bike.
Gennady Padalka, 50, told Russia's Novaya Gazeta newspaper the lack of sharing was lowering the crew's morale.
The veteran cosmonaut said the problem was due to the ISS becoming a more commercial operation.
For several years after his first space mission in 1998, Mr Padalka and his American colleagues worked in total harmony, he told the newspaper.
But space missions became more commercial in 2003 and Moscow started billing Washington for sending its astronauts into space, he said. Other nations responded in kind, he added.
"What is going on has an adverse effect on our work," said Mr Padalka, 50, a veteran of two space missions who is to be the station's next commander.
Padalka complimented the quality of the US amenities on the space station
Before he lifted off to join the ISS crew on Thursday, Mr Padalka had asked whether he could use a US gym to stay fit.
"They told me: 'Yes, you can.' Then they said no," Novaya Gazeta quoted him as saying.
"Then they hold consultations and they approve it again. And now, right before the flight, it turns out again that the answer is negative."
Worse still, the regulations now required US and Russian cosmonauts to eat their own rations, he added.
"They also recommend us to only use national toilets," the newspaper quoted him as saying.
"Cosmonauts are above the ongoing squabble, no matter what officials decide," he told the newspaper. "It's politicians and bureaucrats who can't reach agreement, not us."
The situation may be exacerbated by an increase in the number of astronauts living on the ISS.
Until now only three astronauts lived on the International Space Station at any one time.
But last week, a Russian Soyuz rocket blasted off from Kazakhstan to ferry Mr Padalka and two other crew-members to the ISS. It docked safely on Saturday.
While doubling the number of crew will allow more scientific research to be carried out, it will also mean there will be less room for visitors.
Among the new crew was US billionaire Charles Simonyi, 60, a software tycoon who paid $35m (£24m) for his 13-day trip, during which he will help with research projects and take part in live broadcasts with schools.