NASA and SpaceX early on Monday postponed the launch of two US astronauts, a Russian cosmonaut and a United Arab Emirates crewmate minutes before they were due to lift off from Florida on a flight to the International Space Station.
The US space agency and SpaceX, the private rocket company founded by billionaire Elon Musk, cited a technical glitch concerning the flow of ignition fluid used to help start the spacecraft's engines.
The countdown had seemed to be progressing smoothly until about two and a half minutes before blastoff, when NASA announced on its live webcast that the launch of the four crew members on a six-month science mission would be postponed.
The SpaceX Falcon 9 rocket topped with a Crew Dragon capsule had been scheduled for liftoff at 1:45 a.m. EST (0645 GMT) from NASA's Kennedy Space Center in Cape Canaveral, Florida.
The first backup launch opportunity for the mission was set for early Tuesday, about 24 hours from the initial attempt to get the rocket off the ground.
Neither NASA nor SpaceX immediately said how long it might actually take before they would be ready to try again. Eleventh-hour launch scrubs are fairly routine in the highly complex and risky endeavor of human spaceflight.
Had Monday's launch been a success, it was expected to take the crew about 25 hoursto reach their destination at the International Space Station (ISS), a laboratory orbiting about 250 miles (420 km) above Earth.
Designated Crew 6, the mission will carry the sixth long-duration ISS team that NASA has flown aboard SpaceX since Musk's California-based company began sending American astronauts to orbit in May 2020.