Nasa said on Thursday that the long-delayed launch of Artemis II, the first crewed flyby mission to the moon in more than 50 years, could come as soon as 1 April.

“We are on track for a launch as early as April 1, and we are working toward that date,” Lori Glaze, a senior Nasa official, told a press conference, after technical difficulties delayed a launch originally expected in February.

“It’s a test flight, and it is not without risk, but our team and our hardware are ready,” she said. “Just keep in mind we still have work [to do].”

The US space agency announced in February a sudden revamp of the Artemis programme, including the addition of a test mission before an eventual lunar landing.

The first launch window would be Wednesday 1 April at 6.24pm (22.24 GMT), with several others available in the following days.

“We would anticipate on the order of about four opportunities within that six-day period,” Glaze said.

The Artemis II mission is meant to be the first flyby of the moon in more than half a century.

The rocket will be crewed by three American astronauts – the mission commander, Reid Wiseman, Victor Glover and Christina Koch – and the Canadian astronaut Jeremy Hansen.

After launch, Nasa diagrams indicate Artemis II will circumnavigate Earth before leaving orbit to travel to the moon, without landing, for a lunar flyby before returning to Earth and splashing down in the ocean.

“Exactly how close the Artemis II crew will fly to the moon will depend on when they launch,” ranging from 4,000 to 6,000 miles (6,437 to 9,656 km) above the lunar surface, because the moon will “be in a different spot for each of the possible launch dates”.

The first Artemis flew much closer to the moon – 80 miles above the surface – but Nasa said Artemis II will still go “tens of thousands of miles closer than any human has been in more than 50 years.”

“At this distance the moon will appear to the crew to be about the size of a basketball held at arm’s length.”

The mission is to be followed by Artemis III with the goal of “rendezvous in low-Earth orbit” of at least one lunar lander.

The next phase, Artemis IIII, aims for a lunar landing in early 2028, after the US president, Donald Trump, announced during his first term that he wanted Americans to once again set foot on the moon.