"NASA has executed a flawed acquisition for the Human Landing System program and moved the goalposts at the last minute," Blue Origin said in a statement sent to AFP.

The decision "eliminates opportunities for competition, significantly narrows the supply base, and not only delays, but also endangers America's return to the Moon" by 2024 as the US space agency plans, the private space company said.

"Because of that, we've filed a protest with the GAO," or Government Accountability Office, which audits services for Congress.

NASA announced just over a week ago that it had chosen Tesla founder Elon Musk's company to take its astronauts back to the Moon, awarding SpaceX a $2.9 billion contract to develop the Starship rocket.

But Blue Origin argued that NASA had misjudged the risks involved in choosing SpaceX's "entirely new launch vehicle."

"Starship has no flight heritage or validation of performance, and launch vehicle development is notoriously difficult and takes much longer than anticipated," the complaint said.

Prototypes of the rocket are currently being tested in Texas, but recent tests have ended in spectacular explosions. In addition, Blue Origin said, the space agency's decision to award only one winner rather than two, as had been originally set out in the submissions process, would leave the project at "high risk" because it lacks a back-up plan.

The decision also "creates a potential monopoly for all future NASA exploration missions because there would not be continuing programs for lunar access other than the SpaceX solution," the protest said.

Blue Origin, which had partnered with three big names in the aerospace industry -- Lockheed Martin, Northrop Grumman and Draper -- to respond to NASA's call for tenders, asked the GAO to press NASA to rescind its decision and "resolicit offers against a revised statement of available funds, and conduct discussions with all eligible offerors under the revised requirements."

A spokeswoman for NASA told AFP the space agency had been "notified" that Blue Origin had filed a protest but said they "cannot provide further comment due to pending litigation.

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