Nasa has suspended cooperation with Russia in the latest diplomatic reaction to the ongoing crisis in Ukraine.
But the severing of ties should not affect its joint work on the International Space Station, which is exempt from the ban.
Nasa, which is an agency of the US government and funded by Congress, said in a statement that its work would be suspended with immediate effect:
"Given Russia's ongoing violation of Ukraine's sovereignty and territorial integrity, NASA is suspending the majority of its ongoing engagements with the Russian Federation. NASA and Roscosmos will, however, continue to work together to maintain safe and continuous operation of the International Space Station."
The suspension extends to all email and teleconferencing, except where it relates to the ongoing operation of the space station (and the safety aspects involved in the mission).
Nasa officials are able to attend multi-national meetings where Russian officials are present, however.
Currently Nasa is dependent on Russia for its Soyuz capsules - currently the only space craft which is capable of sending astronauts to the ISS and returning them to Earth. Nasa is working on its own rockets to start sending astronauts to the platform again but says they won't be ready until 2017 - and neither will attempts by private companies to build their own manned orbital craft.
"With the reduced level of funding approved by Congress, we’re now looking at launching from U.S. soil in 2017," Nasa said.Suggest a correction
"The choice here is between fully funding the plan to bring space launches back to America or continuing to send millions of dollars to the Russians. It’s that simple. The Obama Administration chooses to invest in America — and we are hopeful that Congress will do the same."