PARIS, WASHINGTON – Russian Deputy Prime Minister Dmitry Rogozin said May 13 that Moscow would halt the sale of RD-180 and NK-33 rocket engines to the U.S. for the purpose of launching military satellites.

The RD-180 is used to power the first stage of the United Launch Alliance (ULA) Atlas V rocket, while a modified version of the NK-33 – the Aerojet Rocketdyne AJ-26 – provides core propulsion on the first stage of the Orbital Sciences Corp. Antares launch vehicle.

"We will assume that, without guarantees that our engines are used only for launching non-military spacecraft, we won’t be able to deliver them to the U.S.," Rogozin told reporters during a news conference.

ULA, which says it has more than two year’s worth of RD-180 engines in its U.S. inventory, is "not aware of any restrictions," according to a company statement. "If recent news reports are accurate, it affirms that [Space Exploration Technology’s] SpaceX’s irresponsible actions have created unnecessary distractions, threatened U.S. military satellite operations, and undermined our future relationship with the International Space Station." The company is referencing a protest in Federal Claims Court filed April 28 by SpaceX claiming that the Air Force’s five-year, sole-source deal with ULA unfairly cut the company, and its new Falcon 9 v1.1 launcher, out of the competition. The filing prompted a temporary injunction in payments for RD-180 work and thrust the issue into the public debate amid mounting tensions between Washington and Moscow.

"We are hopeful that our two nations will engage in productive conversations over the coming months that will resolve the matter quickly," the company statement says. "ULA and our Department of Defense customers have always prepared contingency plans in the event of a supply disruption [and we] maintain a two-year inventory of engines to enable a smooth transition to our other rocket, Delta, which has all U.S.-produced rocket engines."

The Air Force inked an agreement with ULA, currently a monopoly in the U.S., in December for 36 engine cores, including Atlas V and Delta IV missions. In the meantime, the Air Force is studying options for developing a U.S. alternative to the RD-180 in an effort to curb U.S. reliance on Russia for launching national security payloads.

A supply interruption for the RD-180 is, however, forcing a policy discussion over whether Washington should continue to rely on a Russian engine, pay to establish stateside co-production, invest in a new engine design or mothball Atlas V in favor of onramping SpaceX’s Falcon 9 v1.1 and, eventually, its Falcon Heavy launcher. There is little appetite for the government to support three launch vehicles in the coming years, especially as the Pentagon forges its way through budget cuts and questions on sequestration.

Orbital, which does not yet have U.S. Air Force certification for launching national security missions on Antares, is currently considering a domestic propulsion supplier for the rocket’s first stage.

Rogozin’s announcement, reported May 13 by Russian news agency Interfax, follows a U.S. ban on high-tech exports to Russia if such articles could in some manner benefit the Russian military.

Rogozin, who oversees Russia’s space and defense industries, and who in March was sanctioned by the U.S. Treasury Department over Moscow’s recent annexation of Crimea, also said Russia will suspend U.S. GPS station work on its territory beginning in June if an agreement is not reached to set up Russian Glonass navigation satellite ground stations on U.S. territory.

"We are suspending the work of these stations in Russian territory from June 1," he told the news conference.

However, a U.S. industry source said suspending work on GPS sites in Russia would have no effect on the functioning of the system as the stations Rogozin refers to are used only for monitoring.

Rogozin also warned that Russia would not extend its participation in the International Space Station beyond 2020 as proposed by the Obama administration, which in January unveiled plans to continue operating the orbiting lab through 2024. Rogozin explained that Russia is planning to direct funding toward other prospective space projects.

In a separate statement, Russian space agency Roscosmos said almost 2 trillion rubles ($57 billion) will go to the federal space program for the period 2013-20.

"Overall, 1.8 trillion rubles will be provided from the federal budget to implement the state space program," Roscosmos said.