The Dragon capsule will be the first commercial spacecraft to dock with the International Space Station. (SpaceX illustration)

CAPE CANAVERAL, Fla. (May 19, 2012)--The countdown almost reached zero early Saturday morning for the SpaceX Falcon 9 rocket, which was set to lift off on the first commercial cargo run to the International Space Station.

The engine ignition sequence started, but there was an automatic shutdown by on-board computers, a NASA spokesman said.

So instead of lifting off from Cape Canaveral on a delivery mission to the space station, the rocket remained on its launch pad engulfed in a cloud of engine exhaust.

An engine pressure problem is suspected.

The next launch attempt will be Tuesday, if the problem can be resolved in time.

The rocket’s nine engines were tested extensively at the company’s facility in McGregor west of Waco.

The launch will be the culmination of an effort that started six years ago and came to fruition in December 2008 when NASA awarded a $1.6 billion contract to SpaceX for a rocket and spacecraft to transport cargo to the International Space Station after the U.S. shuttle program ended.

Under the contract, the company’s Falcon 9 launch vehicle and Dragon spacecraft will be used to transport a guaranteed minimum of 44,000 pounds of pressurized and unpressurized cargo to the space station and NASA could order additional missions for a total contract value of as much as $3.1 billion, SpaceX said.

Two years later, in December 2010, SpaceX placed its Dragon capsule in orbit for the first time.

The Dragon circled Earth at speeds of more than 17,000 miles per hour before re-entering the atmosphere three hours later and deploying a parachute to land in the Pacific Ocean, 500 miles off the Mexican coast, marking the first time a commercial business recovered a spacecraft after reentry.

The capsule, incidentally, carried a secret cargo—a wheel of Le Brouere cheese in a container bolted to the floor.

SpaceX said the round of Le Brouere was a tribute to the Monty Python comedy team, which performed an odd, but amusing five-and-a-half minute sketch in which a pedantic and very British customer enters a cheese shop only to discover that cheese was the one thing the shop didn’t seem to have.

Finally in frustration, the customer shoots the proprietor, and then dons a cowboy hat.