The target date for the next attempt to launch Boeing Co's Starliner space capsule on its first crewed test flight has been pushed back to no earlier than May 17, to replace a pressure valve on its booster rocket, NASA said on Tuesday.

The CST-100 Starliner's debut voyage carrying astronauts to the International Space Station (ISS) has been highly anticipated and much-delayed as Boeing scrambles to compete with Elon Musk's SpaceX for a greater share of lucrative NASA business.

The test flight was called off on Monday night with less than two hours left in the countdown after a pressure regulation valve malfunctioned on the upper-stage liquid oxygen tank of the Atlas V rocket that was to launch the new capsule into orbit.

The rocket, a separate component from the Starliner capsule, was furnished for the mission by United Launch Alliance (ULA), a Boeing-Lockheed Martin joint venture.

After Monday night's aborted launch attempt, NASA, Boeing and ULA announced that they would seek to try again as early as Friday, May 10.

But in an update posted Tuesday evening, NASA said more time was needed after ULA "decided to remove and replace" the faulty pressure valve. That will require the rocket to be rolled back to its hangar on Wednesday for repairs, leak checks and other reviews ahead of a second launch attempt, NASA said.

Those operations pushed the potential launch date back another week, NASA said.