In an internal memo, NASA has stated that it will suspend all interaction with the Russian government, in response to Russia's violations of Ukraine's territorial independence (Update: official statement below). Fortunately for U.S. astronauts Rick Mastracchio and Steve Swanson, both currently orbiting on the International Space Station, the two agencies will still cooperate to transport supplies and personnel to and from the ISS.
As The Verge reports, the internal memo states that NASA will suspend all travel to Russia, email or telecommunication, and U.S. visits by Russian government officials. In other words, all employee contact between NASA and Russian space officials is banned, so long as it doesn't affect ISS operations. Such a move has been speculated since the turmoil over the Crimean territory began, but today gives our first indication they plan to act on it.