Photo of an Atlas V rocket launching the New Horizons project into space. NASA/Kim Shiflett A prime SpaceX competitor — United Launch Alliance (ULA) — might be banned from flying one of its most important rockets, which could spell ruin for the company.

Right now, the US Government is determining whether importing Russian-made RD-180 rocket engines — which power ULA's Atlas V rockets — violates sanctions against Russia.

The US first imposed these sanctions on dozens of Russian officials after Russia seized Crimea in 2014, SpaceNews reported.

If the government finds that violation is in play, space company ULA will be unable to purchase new engines with which to launch its Atlas V rockets.

The Atlas V is one of four launch vehicles the ULA uses to carry out missions for government and commercial companies. And it's one of their most popular — ULA's last 11 missions were all conducted on Atlas V rockets.

The only problem is that the main rocket stage runs on Russian RD-180 engines, which are made by the Russian company called NPO Energomash.

And Energomash is run by numerous sanctioned Russia officials, including Deputy Prime Minister Dmitry Rogozin.

"These folks are on the sanctions list, and if the Department of the Treasury comes back and says there's a problem with that relationship, then we have to work with the Congress and others to determine a way ahead," Samuel Greaves, who heads the US Air Force's Space and Missile Systems Center, told Reuters.

The US Air Force stands to lose a lot if RD-180 engine imports are banned because ULA is currently only one of two space companies the Air Force has certified to conduct important national security launches.

The other company is SpaceX.

If ULA loses the launch capability of its Atlas V rockets, it will be more difficult for the company to compete against SpaceX for national security launch contracts — a main source of business for the company.

The evaluations were performed last week in time for a deadline set for this week by Senate Armed Services Committee Chairman John McCain. Therefore, we could know soon whether the Atlas V is grounded, or not.