A spacewalk by two U.S. astronauts was called off on Tuesday morning due to the risk of space debris, NASA announced in a statement.

       NASA astronauts Kayla Barron and Thomas Marshburn were scheduled to leave through the International Space Station's Quest airlock at 5:30 a.m. EST to replace a part on the space station, according to a NASA blogpost.

       Handout/NASA TV/AFP via Getty Images, FILE

       ESA (European Space Agency) astronaut Thomas Pesquet checks cables during the ISS Expedition 65 US Spacewalk # 74 on June 16, 2021. The spacewalk will last over six hours in support of station assembly, maintenance, and upgrades.

       "Marshburn and Barron will work at the Port 1 truss structure, where the antenna is mounted. The antenna recently lost its ability to send signals to Earth via NASA's Tracking and Data Relay Satellite System," NASA said in the blog.

       However, four hours before the scheduled spacewalk, the ISS tweeted that the repair would be delayed until more information was available.

       The source of the debris hasn't been confirmed. Two weeks ago Russia had conducted an anti-satellite test that created a "dangerous" debris field in the orbit.

       MORE: US condemns Russian anti-satellite test it says created 'dangerous' debris field

       Xinhua News Agency via Getty Images, FILE

       Chinese astronaut Liu Boming conducts extravehicular activities out of the space station core module Tianhe at Beijing Aerospace Control Center, on July 4, 2021.

       The spacewalk was scheduled to last 6 1/2 hours and be Barron's first and Marshburn's fifth spacewalk, NASA said.