"Today, we have made a decision to halt the deliveries of rocket engines produced by NPO Energomash to the United States. Let me remind you that these deliveries had been quite intensive somewhere since the mid-1990s," Roscosmos Chief Dmitry Rogozin said in an interview with the Rossiya-24 TV on Thursday. 

United Launch Alliance (ULA), a joint venture between Boeing and Lockheed Martin, uses Russian RD-180 engines to power Atlas V launch vehicle's main propulsion systems. ULA has been developing a new rocket called Vulcan, which would use American-made engines. Those engines, called BE-4s, are being developed by Jeff Bezos' Blue Origin and are almost ready for testing. ULA CEO Tory Bruno told The Verge, "the very first Vulcan flight, slated to take place this year."