On May 13, Dmitry Rogozin, the bureaucrat who leads Russia's defense industry, announced two retaliatory actions against the U.S. in response to the sanctions being placed on Russia over the Ukraine crisis. First, Russia will no longer allow Americans to ride on their rockets in order to gain access to the International Space Station (ISS) after 2020. Secondly, effective immediately, Russia will stop selling their RD-180 and NK-33 rocket engines to American companies which are currently being used to launch commercial and military satellites.
Certainly, this announcement seems to spell the end of our involvement in the International Space Station after 2020 because, since the ending of our Space Shuttle program in 2011, the U.S. has had no manned space capability. This is a result of Obama killing Shuttle replacement as a budget cutting effort in 2010. In actuality, America is scheduled to return to manned low-earth orbit missions in 2017 in a NASA program called Commercial Crew Program (CCP).
Unlike the original replacement program, which would have been fully NASA funded and controlled, the CCP is intended to be more of a civilian based system. The program has two crew vehicles: a CST-100 capsule and the Dream Chaser space plane. In terms of launch vehicles, both crew vehicles are capable of being launched by either the Atlas V, Delta IV, or the Falcon 9 rockets. Of those, only the Atlas V rocket uses the embargoed Russian engines. Even so, the makers of Atlas V still have enough stockpiled Russian engines to keep that vehicle operating for another two years. Beyond that, I am quite sure that the Atlas V will be retrofitted with U.S. made engines; once the Russian supplies are depleted.
In essence, Russia's attempts at retaliation are quite foolish. My guess is that Putin cooked this whole thing up for public consumption in mother Russia. This way, he is seen as a strong leader, capable of taking strong actions against Obama and his sanctions.
Russia casts doubt on US' future with the ISS over Ukraine sanctions: http://www.foxnews.com/world/2014/05/13/russia-casts-doubt-on-us-future-with-iss-over-ukraine-sanctions/
NASA's Commercial Crew Program: http://en.wikipedia.org/wiki/Commercial_Crew_Development
Dream Chaser: http://en.wikipedia.org/wiki/Dream_Chaser
ATLAS V Rocket: http://en.wikipedia.org/wiki/Commercial_Crew_Development