The launch of a privately owned Falcon 9 rocket from Cape Canaveral Air Force Station was delayed today when a computer detected a possible problem with one of the rocket's engines.
Preparations for the company's trial cargo run to the International Space Station proceeded smoothly until 4:55am local time when, instead of the Falcon 9 rocket's main engines igniting, an onboard computer scrubbed the launch.
"Liftoff - we've had a cutoff. Liftoff did not occur," said NASA launch commentator George Diller.
A few minutes later a SpaceX official reported the cause of the delay - a high-pressure reading in one of the engine's chambers. With only a one-second launch opportunity today, SpaceX had no time to try to sort out the problem.
The company's next opportunity to launch is on Tuesday.
The unmanned rocket, carrying a Dragon cargo capsule, will try to reach the International Space Station.
SpaceX is one of two firms hired by NASA to fly cargo to the $100bn orbital outpost, which is owned by the United States, Russia, Europe, Japan and Canada.
Since the space shuttles were retired last year, NASA has had no way to reach the station and is dependent on its partner countries to fly cargo and crew. It hopes to change that by buying rides commercially from US companies.