A technical problem has forced the company SpaceX to abort what would have been the first launch of a privately owned capsule to the International Space Station.
The pre-dawn launch of the Dragon Capsule from Cape Canaveral, Florida was scrubbed half a second before it was to occur on Saturday.
Initial plans are to try again Tuesday morning.
The capsule is on a long, thin white rocket owned by SpaceX. It is carrying supplies for the International Space Station.
SpaceX president Gwynne Shotwell says the company decided to stop the launch after a computer detected high chamber pressure in one of the engines. She said the cause is not clear.
"Engine 5 was trending high, but it hit the abort limit at T-minus-point 5," Shotwell said.
Shotwell insisted, "this is not a failure," because all nine of the rocket's engines are needed for lift-off.
NASA/SpaceX press conference on failed launch
The Dragon Capsule is carrying 544 kilograms of cargo for what would be a test flight.
The cargo is not considered essential for the space station crew.
SpaceX received more than $380 million in funding from the U.S. space agency, NASA, which retired its space shuttle fleet last year.
Video of failed SpaceX Launch