NASA has further postponed the launch of the space shuttle, Atlantis, due to a problem with a sensor in the spacecraft's external fuel tank.
The mission was due to take off from Florida to resume construction of the International Space Station.
It had already been delayed nearly two weeks due to weather problems and a technical glitch with a power generator on the spacecraft.
The US space agency has said it would make another attempt to fly the shuttle on Saturday.
The launch is to be the first construction mission to the ISS since the 2003 Columbia disaster.
