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(CNN)SpaceX and NASA have called off an astronaut launch to the International Space Station after an issue with the rocket's ground system was detected.
With about two minutes left on the countdown clock, the launch was called off because of a problem related to the TEA-TEB ignition fluid, which is used to ignite the SpaceX Falcon 9's rocket engines at liftoff.
The decision to wave off the launch was made "out of an abundance of caution," said Kate Tice, a SpaceX systems engineer, in commentary on Monday's webcast.
The four astronauts exited the spacecraft after waiting for it to be drained of its fuel.
The four astronauts, who were strapped into their Crew Dragon capsule atop the rocket in the hours leading up to launch, disembarked from the spacecraft after waiting for the 230-foot-tall (70-meter) rocket to be drained of its fuel. They'll stay on site at Kennedy Space Center until the next launch attempt.
NASA said it would now look to launch the SpaceX Crew-6 mission at 12:34 a.m. EST Thursday, March 2 "pending resolution of the technical issue preventing Monday's launch."
The agency said it would skip a launch opportunity on Tuesday because of an unfavorable weather forecast.
"I'm proud of the NASA and SpaceX teams' focus and dedication to keeping Crew-6 safe," NASA's Administrator Bill Nelson said in a blog post.
"Human spaceflight is an inherently risky endeavor and, as always, we will fly when we are ready."
The SpaceX Falcon 9 rocket and Crew Dragon capsule were slated to lift off from NASA's Kennedy Space Center in Cape Canaveral, Florida, at 1:45 a.m. ET Monday. But the clock was stopped by engineers that oversee the ground systems with less than three minutes left.
This mission is expected to mark the seventh astronaut flight SpaceX has carried out on NASA's behalf since 2020.
The SpaceX Falcon 9 rocket is pictured shortly after the launch was called off on Monday at NASA's Kennedy Space Center in Florida.