United Launch Alliance (ULA), a Boeing-Lockheed venture, has sought a replacement engine for its Atlas 5 rockets, used to launch various US military and spy satellites, Reuters reported.

The Russian-made RD-180 currently powers the Atlas 5, but tensions between Russia and the United States over unrest in Ukraine has led to some concerns that Russia could curb deliveries of the RD-180, according to US officials, who want to find and fun an American alternative in the Pentagon’s 2016 budget.

Boeing and Lockheed officials declined to comment, and Blue Origin and ULA officials were not immediate available for comment, Reuters reported. The companies are expected to announce the deal on Wednesday.

Boeing will likely win most of the work on the engine, the Wall Street Journal reported, as its commercial crew capsule - also launched by the Atlas 5 - would benefit from a new US rocket engine, industry officials said.

US officials were seeking a government-industry alliance to produce a US rocket engine to reduce reliance on Russian engines, Pentagon acquisition head Frank Kendall said this month.

Russia continued to deliver RD-180 to the US despite the concerns. Two engines arrived last month, with three more due in the fall.

ULA has enough RD-180 engines to last two years, it says. It has an $11 billion contract with the US Air Force for 36 launches, though Space Exploration Technologies Corp., or SpaceX - founded and owned by Elon Musk - has sued in federal claims court to be allowed to compete for an increased share of that work.

SpaceX is seeking Air Force certification of its Falcon 9 rocket, making Musk’s company a competitor for Bezos’ Blue Origin. The certification was due by the end of this year, though US officials say it may take longer after the explosion of a SpaceX experimental rocket that uses the same engine as the Falcon 9.

SpaceX is also competing with Boeing and others for a NASA contract to move astronauts to and from the international space station. NASA is supposed to award the contract to one or multiple bidders on Tuesday, sources said.