The launch of a SpaceX rocket ship with two Nasa astronauts on a history-making flight into orbit was called off with less than 17 minutes to go in the countdown on Wednesday because of thunderclouds and the danger of lightning.

Lift-off was rescheduled for Saturday afternoon.

The spacecraft — designed, built and owned by SpaceX — was set to blast off in the afternoon for the International Space Station, ushering in a new era in commercial space flight and putting Nasa back in the business of launching astronauts from US soil for the first time in nearly a decade.

But thunderstorms for much of the day threatened to force a postponement, and the word finally came down that the atmosphere was so electrically charged that the spacecraft with Nasa astronauts Doug Hurley and Bob Behnken aboard was in danger of getting hit by a bolt of lightning.

“No launch for today — safety for our crew members @Astro_Doug and @AstroBehnken is our top priority,” Nasa administrator Jim Bridenstine tweeted, using a lightning emoji.

The two men were scheduled to ride into orbit aboard the SpaceX’s sleek, bullet-shaped Dragon capsule on top of a Falcon 9 rocket, taking off from the same launch pad used during the Apollo moon missions a half-century ago. Both President Donald Trump and Vice President Mike Pence had arrived to watch.

The flight — the long-held dream of SpaceX founder Elon Musk — would have marked the first time a private company sent humans into orbit.

It would also have been the first time in nearly a decade that the US launched astronauts into orbit from its soil. Ever since the space shuttle was retired in 2011, NASA has relied on Russian spaceships launched from Kazakhstan to take US astronauts to and from the space station.

During the day, thunder could be heard as the astronauts made their way to the pad at Nasa’s Kennedy Space Center, and a tornado warning was issued moments after they climbed into their capsule.

“We could see some raindrops on the windows and just figured that whatever it was, was too close to the launch pad at the time we needed it not to be,” Hurley, the spacecraft commander, said after the flight was scrubbed. “Understand that everybody’s probably a little bit bummed out. That's just part of the deal. ... We’ll do it again, I think, on Saturday.”

“Appreciate your resilience sitting there in the vehicle,” a controller replied.

Behnken responded: “Nothing better than being prime crew on a new spaceship.”

The astronauts had to remain strapped in their seats until all the fuel in their rocket was unloaded and the emergency escape system was disarmed.

The mission would put Musk and SpaceX in the same league as only three space-faring countries — Russia, the US and China, all of which have sent astronauts into orbit.

“What today is about is reigniting the dream of space and getting people fired up about the future,” Musk said in a Nasa interview before the flight was scrubbed.

The space agency also estimated 1.7 million people were watching the launch preparations online during the afternoon.