United Launch Alliance, the Boeing-Lockheed Martin joint venture responsible for the rocket, initially said the launch would be delayed to at least May 10.
But further analysis revealed that the valve was too worn and needed to be replaced. The rocket will be taken back to its hangar for repairs.
“NASA's Boeing Crew Flight Test is now on target to launch no later than 6:16 p.m. EDT on Friday, May 17,” the U.S. space agency said in a blog post.
The post said Wilmore and Williams will remain in quarantine in crew quarters at NASA's Kennedy Space Center.
NASA is confident in the success of Starliner as it hopes for a second commercial vehicle to carry crews to the orbital outpost.
Elon Musk's SpaceX achieved this feat with its Dragon capsule in 2020, ending nearly a decade-long reliance on Russian rockets following the end of the Space Shuttle program.
