Colossal rocket Artemis I had been due to launch on Monday - marking the next step in putting humankind on the moon - but an engine cooling issue prevented it from taking off.
NASA now says it will make a second attempt on Saturday evening, in a two-hour launch from 7.17pm BST.
However, the weather forecast shows just a 40 per cent chance of favourable conditions that day, while the US space agency acknowledged some outstanding technical issues remain.
More than 50 years after Apollo’s last lunar mission saw humans reach the moon, the launch of the Artemis programme aims to prove people can make longer and more sustainable trips there.
The Artemis I test flight had been due to take off from the Kennedy Space Centre in Cape Canaveral, Florida, during a two-hour window after 1.33pm BST on Monday.
— NASA (@NASA) August 30, 2022
It was called off by the launch director moments before due to a temperature problem in one of the engines.
Michael Sarafin, Artemis mission manager, said the team also encountered issues over the weekend and on Monday, including lightning strikes and a fuel leak.
US vice president Kamala Harris was among those at the space centre awaiting take-off on Monday, and Nasa administrator Bill Nelson said she was “pumped the entire time”.
The 322ft (98m) tall Space Launch System (SLS) rocket, which is the world’s most powerful rocket to date, is due to take the Orion capsule, powered by the Airbus-built European Service Module (ESM), into the Moon’s orbit.
The UK is part of the Artemis programme, making contributions to the Lunar Gateway – a space station currently in development with the European Space Agency – working alongside the US, Europe, Canada and Japan.
UK Space Agency chief executive Paul Bate said that when the rocket does eventually launch “it is going to be wild”.
Writing on Twitter following Monday’s attempt, he said: “Not easy, this rocket science.
“But that’s the point, right … we are pushing the boundaries of human knowledge and discovery.
“And when we do launch, it is going to be wild. Onwards to the Moon, Mars and beyond.”
The flight will carry mannequins rather than astronauts, and is the first in Nasa’s Artemis programme.
There will be people on board for subsequent missions, with the first crewed flight into space scheduled for 2024.
It will also assess whether some infrastructure can be built on and around the Moon, allowing humans to survive on another planetary body.
The mission is set to last 42 days, three hours and 20 minutes, and will see the rocket travel 1.3 million miles.