The maiden liftoff of a new American rocket called Vulcan Centaur has been delayed from Christmas Eve to January 8, United Launch Alliance, the company developing it, said Thursday.

The postponement stems from last-minute technical snags but ULA's CEO Tory Bruno said on X, formerly Twitter, that a recent dress rehearsal on the launch pad went well.

The rocket will be carrying a private lunar lander, developed by the startup Astrobotic, which could become the first such private craft to touch down on the moon and the first American robot to land on the surface since the Apollo program ended in 1972.

"This is sort of, in a way, the first giant step in the campaign for the US, and for all of our friends, to go back to the moon, eventually with people," Bruno told AFP in an interview last week.

"It's a pretty big deal to have a payload at all, let alone one that goes to the surface of the moon," he added.

"We wanted to do something really important and we have a lot of confidence, obviously, in the design of our rocket," Bruno said.

SpaceX is standing down from attempting to launch its powerhouse Falcon Heavy for now citing the need for "systems checkouts" while weather would have been an issue the next couple of days, and has already delayed a Falcon 9 launch as well.

After already delaying a Sunday attempt to launch Falcon Heavy from Kennedy Space Center's Launch Pad 39-A because of weather and then scrubbing a Monday night attempt less than an hour before its planned liftoff because of a "ground side issue," SpaceX had announced it would try again Wednesday.

But late Tuesday, it called off those plans.

"We are standing down from tomorrow's Falcon Heavy launch of USSF-52 to perform additional system checkouts," the company posted to X. "The payload remains healthy while teams work toward the next best launch opportunity. We're also keeping an eye on the weather and will announce a new launch date once confirmed with the Range."

USSF-52 is a mission to send up the Space Force's secretive mini shuttle, the X-37B Orbital Test Vehicle built by Boeing, on what would be the spacecraft's seventh trip to orbit.