The countdown was halted with just two minutes remaining until liftoff from Kennedy Space Center. With just a split second to blast off, there was no time to deal with the problem, which involved the engine ignition system.

SpaceX did not immediately say when it would try again. The next attempt could come as early as Tuesday, although poor weather was forecast.

Strapped into the capsule atop the Falcon rocket were two NASA astronauts, one Russian cosmonaut and one astronaut from the United Arab Emirates.

When informed by SpaceX that the fuel would start to be drained from the rocket, commander Stephen Bowen replied: “We'll be sitting here waiting.” It was expected to take nearly an hour.

Bowen and his crew — including the first astronaut from the United Arab Emirates assigned to a monthslong mission, Sultan al-Neyadi — will replace another SpaceX crew that flew to the space station in October.