NASA has suspended contact with Russian government representatives, citing ongoing violations of Ukraine's sovereignty and territorial integrity, according to an internal letter written by a top official on Wednesday.
The authenticity of the letter has been confirmed by Fox News.
“This suspension includes NASA travel to Russia and visits by Russian Government representatives to NASA facilities, bilateral meetings, email, and teleconferences or videoconferences,” states the letter, which was written by Michael F. O'Brien, NASA’s associate administrator for international and interagency relations.
However, ongoing activities at the International Space Station (ISS) have been exempted from the rules, as well as “multilateral meetings held outside of Russia that may include Russian participation.”
There are currently two Americans onboard the ISS.
NASA told Fox News that it will release a statement on the situation soon.
In early March, NASA Administrator Charles Bolden insisted that the U.S. and Russia’s space partnership was not being strained over tensions in Ukraine.
"Right now, everything is normal in our relationship with the Russians," Bolden said at the time. "I think people lose track of the fact that we have occupied the International Space Station now for 13 consecutive years uninterrupted, and that has been through multiple international crises."
The U.S. relies on the Russian Souyez rockets for all manned trips to and from space. NASA signed an agreement with Russia last April, governing six flights through 2017, at a cost of $70.7 million per seat.
Amid the crisis in Crimea, there is growing concern over the U.S.'s reliance on Russia for human transport to and from the International Space Station since retiring the American space shuttle program.