Space shuttle Discovery will not launch until late next week at the earliest, say space experts at Nasa.
They say the flight will only go ahead if engineers are "lucky" in isolating the problem which caused Wednesday's launch to be cancelled.
It was aborted due to a fuel tank problem. The astronauts were already strapped-in and ready to blast off.
This will be the first shuttle flight since the loss of Columbia and its crew of seven in February 2003.
If Discovery does not take off this month it is likely to be grounded until September.
Loads of extra safety checks were brought in after the Columbia disaster, and Nasa experts are being extra careful about the Discovery launch.
Discovery will carry a crew of seven to the International Space Station with supplies and parts.