This evening's planned launch of the space shuttle, Discovery, from Cape Canaveral in Florida has been postponed due to a technical problem.
A NASA spokesperson said there was a low-level fuel cut-off problem.
The system is designed to prevent the shuttle from using its full power during ascent.
It remains unclear whether NASA will attempt lift-off later this week.
It was due to be the first manned shuttle flight since the Columbia disaster in 2003 in which seven astronauts died.
Just hours before the scheduled lift-off, NASA said the chances weather would prevent the launch rose to 60%, from 40% earlier in the day.
The launch was scheduled for 8.50pm Irish time.
