NASA may delay its mission to send astronauts to the moon for the first time in more than half a century after discovering a fault with its rocket.
Artemis II has been due to blast off from Florida's Kennedy Space Center from as early as March.
On Friday night, however, NASA discovered that the flow of helium - which is required for launch - to the rocket had been interrupted during a key part of the preparation process.
A NASA spokesperson said: "This will almost assuredly impact the March launch window."
Before the setback, the agency had announced that it was targeting 6 March to launch four astronauts around the moon and back.
The crew includes three US astronauts - Reid Wiseman, Victor Glover and Christina Koch - and Canadian Jeremy Hansen.
They would become the first astronauts to fly to the moon since Apollo 17 in 1972 and make the farthest human flight into space ever.
Read more:
Everything to know about Artemis II
There are no plans for the mission to land on its surface, however.
Artemis II is a precursor to NASA's planned astronaut moon landing with Artemis III, which is scheduled for 2028.
The Artemis missions are part of NASA's long-term plans to build a space station - called Lunar Gateway - where astronauts will be able to live and work and prepare for missions to Mars.
A first rehearsal for the launch earlier this month was disrupted after a hydrogen leak was discovered.
But a second test was completed on Thursday without any leaks identified after technicians replaced two seals, which launch director Charlie Blackwell-Thompson described as "a big step in us earning our right to fly".
When the 10-day mission is able to go ahead, it will see the crew testing life support, navigation, and communication systems to confirm everything operates as it should in deep space.
The capsule will then enter Earth's high orbit where the crew will manually pilot Orion before control is handed back to controllers at NASA's Johnson Space Center in Houston, Texas.
The astronauts will then spend four days circling the moon, travelling approximately 4,600 miles beyond its far side before returning to Earth and splashing down in the Pacific Ocean.
(c) Sky News 2026: NASA says moon mission could be delayed after discovering rocket fault
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