"We had a United Space Alliance worker fall at the pad. NASA emergency medical personnel responded but were unable to revive him," spokeswoman Candrea Thomas told AFP. "The incident is under investigation."

United Space Alliance chief executive Virginia Barnes identified the employee as engineer James Vanover.

"Our focus right now is on providing support for the family, and for his co-workers," Barnes said.

"We are also providing our full support to investigating officials in order to determine the cause of the incident as quickly as possible. Until that investigation is complete, it would be inappropriate to provide further comment on the details."

Operations at the Kennedy Space Center launch pad were suspended for the rest of the day.
The shuttle Endeavour was rolled out to the launch pad last week and is set to blast off from Kennedy Space Center on April 19, becoming the second shuttle to embark on its final voyage to the International Space Station.

Discovery ended its last mission into orbit last week and is soon headed for a museum. The final shuttle launch by Atlantis is scheduled for late June.

Thousands of employees of NASA and its contracting agencies have already been laid off and thousands more are set to lose their jobs when the US space shuttle program officially ends later this year.