LOS ANGELES - NASA and Boeing postponed the launch of the first crewed mission of Starliner spacecraft on Monday due to technical issues.

The spacecraft was scheduled to launch on a United Launch Alliance Atlas V rocket at 10:34 pm Eastern Time Monday (0234 GMT Tuesday) from Space Launch Complex-41 at Cape Canaveral Space Force Station in the US state of Florida.

The flight test will carry NASA astronauts Butch Wilmore and Suni Williams to the International Space Station.

The launch was scrubbed as teams were evaluating an oxygen relief valve on the Centaur upper stage on the Atlas V rocket, according to NASA. The two astronauts have exited Starliner and will return to crew quarters.

This mission, dubbed the Crew Flight Test, could be the final major milestone before NASA deems Boeing's spacecraft ready for routine operations as part of the federal agency's Commercial Crew Program.