Blue Origin, the space rocket company backed by billionaire Jeff Bezos, is formally challenging the $2.9 billion moon lander contract awarded by NASA to rival Elon Musk's SpaceX.
The two richest men in the world have been sparring in a tightly fought global space race, vying for contracts from government agencies and businesses.
Blue Origin said on Monday it had filed a protest with the federal Government Accountability Office, accusing NASA of moving the goalposts for contract bidders at the last minute.
Musk fired back with a tweet that said: "Can't get it up (to orbit) lol."
He did not elaborate on the tweet, but pasted a screenshot of a 2019 report about Bezos unveiling Blue Origin's moon lander on the same Twitter thread.
Blue Origin has fallen far behind SpaceX and United Launch Alliance (ULA) on orbital transportation, losing out on billions of dollars' worth of U.S. national security launch contracts that begin in 2022. ULA is a joint venture of Boeing Co and Lockheed Martin Corp
The company was dealt another blow earlier this month, when NASA awarded SpaceX the contract to build a spaceship to deliver astronauts to the moon as early as 2024, choosing Musk's company over Blue Origin and defense contractor Dynetics Inc.
The sought-after project aims to put humans back on the moon for the first time since 1972.
"NASA has executed a flawed acquisition for the Human Landing System program and moved the goalposts at the last minute," Blue Origin said in an emailed statement.
"Their decision eliminates opportunities for competition, significantly narrows the supply base, and not only delays, but also endangers America's return to the moon. Because of that, we've filed a protest with the GAO."
Musk's SpaceX bid alone while Amazon.comfounder Bezos' Blue Origin partnered with Lockheed Martin Corp, Northrop Grumman Corp and Draper.
The filing of the 50-page protest by Blue Origin was reported earlier by the New York Times.