Officials announced the postponement Monday, less than 24 hours before Mark Vande Hei was supposed to float outside.
Vande Hei is dealing with "a minor medical issue," officials said in a statement. It's not an emergency, they noted, but didn't provide any further details.
Vande Hei, 54, a retired Army colonel, has been at the space station since April and is expected to remain there until next spring for a full one-year mission. This is his second station stay.
He and Japanese astronaut Akihiko Hoshide were supposed to venture out Tuesday to install a bracket for new solar wings. NASA said the work can wait.
The spacewalk will be rescheduled after this weekend's planned supply run by SpaceX and a September series of spacewalks on the Russian side of the orbiting lab, according to NASA.
Explore further
© 2021 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed without permission.