A leaked memo from NASA HQ this morning instructs NASA employees and contractors to sever communication with Russian government representatives due to Russia's "ongoing violation of Ukraine's sovereignty and territorial integrity." NASA Watch notes that this move comes less than a month after NASA administrator Charles Bolden assured the public that the situation in Ukraine's Crimean peninsula wouldn't disrupt space cooperation between the United States and Russia.

The prohibition does lay out a specific exemption for International Space Station operational activities, which is important since the ISS can't function without some cooperation between US and Russian ground control. There's also the matter of the station's crew being composed of both American and Russian personnel who have to live and work together to keep the flying laboratory operational.

(Update: though NASA has yet to issue a statement, NBC and Fox News are both reporting that NASA has confirmed the e-mail's authenticity. Further, astronaut Chris Hadfield has linked to the e-mail on his Twitter account, emphasizing that ISS operations are exempt.)

Ars has reached out independently to NASA's public affairs office to confirm the e-mail's authenticity, and the agency's official response is quoted below.

NASA currently depends wholly on Russia for getting astronauts into orbit, and the collaboration between NASA and Russia has been quite deep for more than a decade. Russian personnel in NASA facilities is a common sight, at least at NASA centers dealing with manned space flight like the Johnson Space Center. The two nations are the primary members of a large—and unfortunately fragile—international partnership that oversees the operations of the International Space Station.

Historically, the interaction between NASA and Russia has been firmly amicable; for the tensions over Crimea to leak into that relationship is truly ominous. If the exemption on ISS operations is revoked, the International Space Station would almost certainly have to be de-crewed (though that action would require the US crew to depart using Russian spacecraft, which would be recovered by Russian ground teams).

Update, 19:36 CDT: NASA has released an official statement on the issue:

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. NASA is laser focused on a plan to return human spaceflight launches to American soil, and end our reliance on Russia to get into space. This has been a top priority of the Obama Administration’s for the past five years, and had our plan been fully funded, we would have returned American human spaceflight launches – and the jobs they support – back to the United States next year. With the reduced level of funding approved by Congress, we’re now looking at launching from U.S. soil in 2017. 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.

The full text of the original leaked e-mail is reproduced below, via SpaceRef: