After NASA granted a lunar lander contract to rival SpaceX, Jeff Bezos' Blue Origin is suing the US government.

The complaint, which was filed in federal court and is now sealed, is thought to be a continuation of the company's accusation that the agency awarded the $2.9 billion contract to Elon Musk's SpaceX incorrectly earlier this year.

Blue Origin plans to "remedy the flaws in the acquisition process found in NASA's Human Landing System" according to a spokeswoman.

"We firmly believe that the issues identified in this procurement and its outcomes must be addressed to restore fairness, create competition, and ensure a safe return to the Moon for America," they continued.

SpaceX, Blue Origin, and Dynetics were bidding for two contracts, but NASA opted to award only one contract after financing from Congress fell short of expectations.

NASA's Artemis program, which intends to return humans to the moon for the first time since 1972, gave SpaceX a contract in April to develop a spacecraft to transport astronauts to the lunar surface.

Last month, Blue Origin filed a protest, but the Government Accountability Office backed NASA in its choice to select a single bidder.

NASA should have given more than one award, according to Dynetics.

NASA has until October 12 to reply to Blue Origin's lawsuit.

"NASA officials are currently reviewing details of the case," the agency added.

"With our partners, we will go to the Moon and stay to enable science investigations, develop new technology, and create high paying jobs for the greater good and in preparation to send astronauts to Mars." says the statement.

Jeff Bezos, who also built Amazon, the online marketplace that made him a multibillionaire, founded Blue Origin.