The United States' leading cargo transport company for the International Space Station is challenging the U.S. Air Force's award of a multi-billion-dollar, non-compete contract for 36 rocket launches to two long-time aerospace contractors, Lockheed Martin and Boeing, under the United Launch Alliance partnership.

Space Exploration Technologies Corporation, more commonly known as SpaceX, indicated on Friday it has filed a lawsuit to protest the the satellite-delivery contract, announced earlier this year, which "essentially blocks companies like SpaceX from competing for national security launches," SpaceX Chief Executive Elon Musk said at a press briefing in Washington, D.C.

Based in Hawthorne, Calif., SpaceX is in the process of getting its Falcon 9 rockets -- which are already used in missions the company flies for the National Aeronautics and Space Administration -- certified to fly payloads for the U.S. military.

So far, the Air Force has certified one of three Falcon flights required before SpaceX can compete for military missions, according to Reuters.

Musk emphasized the legal action was not aimed at compelling the Air Force to simply give SpaceX the contract instead, but rather allow the award process to be a real contest between technologies and hard numbers.

"SpaceX is not saying that these launches should be awarded to us," he said. "We're just protesting and saying that these launches should be competed. If we compete and lose, that's fine, but why were they not even competed? That just doesn't make sense."

Musk announced SpaceX would likely be able to fly military payloads for around $100 million apiece, about 75 percent less than the price the U.S. pays now for rides on ULA's Atlas and Delta rockets.

"The ULA rockets are basically about four times more expensive than ours, so this contract is costing the U.S. taxpayers billions of dollars for no reason," said Musk, who also questioned during the press event why the U.S. government was willing to pay so much more for the ULA rockets, built by a Russian aerospace manufacturer, especially amid the international crisis spurred by Russia's invasion of Ukraine's Crimean peninsula -- and apparent now in asserting control as well over eastern Ukraine.

Musk noted that the United Launch Alliance's Atlas rocket uses Russian-made RD-180 engines and that individuals subject of the U.S. sanctions over the Ukraine actions include Dmitry Rogozin, Russia's deputy prime minister and also head of the country's space program.

"How is it that we're sending hundreds of millions of U.S. taxpayer money at a time when Russia is in the process of invading Ukraine?" Musk asked. "It would be hard to imagine some way that Dmitry Rogozin is not benefiting personally from the dollars that are being sent there."

The Air Force said it had no immediate comment on SpaceX's lawsuit, which was filed in the U.S. Court of Federal Claims, although an ongoing review of the RD-180 engine issue was expected to finish up May 1.

Air Force Secretary Deborah James told Congress earlier this month that she was committed to improving the level of competition, but that SpaceX and other market entrants needed to prove they could safely launch important national security satellites, which often cost upwards of $1 billion to build.