The diplomatic standoff between Russia and the USA over events in Ukraine has dented the countries’ longstanding collaboration in spaceflight, with Russia effectively cutting off supplies of rocket motors critical to US military and civilian launches.

Russia, citing “the US policy of imposing sanctions”, has also threatened to deny the USA use of 11 ground stations on Russian territory which support its GPS satellite navigation constellation, unless the USA reverses course and grants a longstanding Russian request to site in the USA a number of ground stations for its GLONASS constellation.

And, according to a statement issued by Russian deputy prime minister Dmitry Rogozin and Roscosmos space agency head Oleg Ostapenko, while Russia will honour all commitments for 2014 commercial spacecraft launches by its Proton vehicles, of 2015 and beyond they said merely: “We are holding talks.”

Rogozin pointed to “economic difficulties” experienced by Russian launch vehicle producers owing to a US policy of preventing Russia from taking delivery of spacecraft to be launched by Russian rockets, “under the pretext that these spacecraft, including EU-made ones, contain US electronics”.

Though Rogozin called sanctions a “boomerang” and “like releasing a bull in a china shop”, Ostapenko stressed that regarding collaborative research he has had talks with NASA and the European Space Agency and “both assure us that the programmes will not be curtailed, and we hope that this work will continue.”

The move, outlined in a 13 May briefing and specifically banning export of RD-180 and NK-33 rocket engines that might be used for any non-commercial payload, has no immediate consequences but poses medium-term headaches for NASA and the US military. Since the retirement of the Space Shuttle fleet in 2011, the US military in particular has been heavily reliant on NPO Energomash-made RD-180s, which power the Atlas V rocket made by Boeing-Lockheed Martin joint venture United Launch Alliance. NASA also relies on Atlas V, with high-profile launches including the 2011 flight of its Curiosity Mars rover.

In a statement, ULA said it was “not aware of any restrictions” but it maintains a “two-year inventory of engines to enable a smooth transition to our other rocket, Delta, which has all US-produced rocket engines.”

For Orbital, the implications of an NK-33 ban are unclear. The engines used in the Antares rocket it supplies to NASA for Space Station resupply missions are modified in the USA by Aerojet, and rebranded AJ26. Aerojet is understood to be in position to supply engines for Orbital’s 16 contracted NASA launches, and had a further stockpile of some 23 engines that need remedial work before modification.

However, the apparent ban on NK-33 sales would appear to scupper attempts by Aerojet to work with Kuznetsov to re-start production and ensure the long-term viability of the Antares programme.

One immediate impact of Russia’s reprisal looks to be the heating up of a dispute involving ULA and SpaceX, which has instigated legal action in a bid to force the US government to open to competitive tender a series of national security payload launches granted to ULA on a sole-source basis. SpaceX contends that its Falcon 9 rocket, or in-development Falcon 9 Heavy, could provide the service for less than half the cost.

According to ULA, however, “if recent news reports [of Russian sanctions] are accurate, it affirms that SpaceX’s irresponsible actions have created unnecessary distractions, threatened US military satellite operations, and undermined our future relationship with the International Space Station.” SpaceX did not respond to a request for comment.

Reports of a clash over the ISS appear, however, to be premature. According to the European Space Agency, all ISS partners including Russia continue to honour agreements to run the station until 2020. Extension beyond 2020, says ESA, “is currently under evaluation” and a decision is not needed before 2016-2017.

NASA, in any case, appears to be working on the assumption that the station will certainly have reached the end of its life by “the early 2020s”. Speaking at the Royal Aeronautical Society in London on 14 March about the agency’s “roadmap” to send scientist-astronauts to Mars in 2035 as a large international effort, NASA chief scientist Ellen Stofan said the agency expects at that time to be able to divert funds that would no longer be spent maintaining and exploiting the ISS to other Mars-preparatory missions.

The European Space Agency is already watching the crisis carefully, should unrest in Ukraine disrupt supply of the RD-869 restartable rocket motor, which forms the fourth-stage propulsion unit of its Vega light launcher. The RD-869 is built by Yuzhnoye in Dnipropetrovsk, just east of the Dnieper river that runs north-south through the country to the Black Sea.