NASA said Monday it was opening the marquee U.S. moon landing contract to other bidders because Elon Musk's SpaceX has experienced mounting delays with its Starship lunar lander.

The move paves the way for rivals such as Jeff Bezos' Blue Origin to snatch a high-profile mission to land the first astronauts on the moon in half a century.

"I'm in the process of opening that contract up. I think we'll see companies like Blue get involved, and maybe others," the U.S. space agency's acting chief Sean Duffy, who also serves as U.S. Transportation Secretary, told Fox News' "Fox & Friends" program.