CAPE CANAVAREL, Florida, the United States, July 13 (Xinhuanet) --NASA called off the planned launch of Shuttle Discovery on Wednesday due to a faulty fuel gauge on the external tank, barely 3 hours before the countdown.

    The US space agency did not announce a new liftoff date.

    "The Return to Flight launch of Space Shuttle Discovery has been postponed due to an issue with a low-level fuel cutoff sensor onboard the vehicle," said NASA in a statement.

    The sensor protects an orbiter's main engines by triggering them to shut down in the event fuel runs unexpectedly low. Mission managers are currently assessing the problem, NASA said. It did not disclose more information.

    NASA's Return to Flight Mission, the first Shuttle mission since the Columbia's tragedy on Feb.1 2003, was previously scheduled for 3:51 p.m. (local time ) July 13. Enditem