Bush was already on board the Boeing 747 and ready to take off for the state capital Charleston, where he was to give a speech marking America's Independence Day.

Bush had been due to leave on the hour-long trip at 9:30 am (1430 GMT) from Hagerstown, Maryland -- an airport near the presidential retreat Camp David, where he spent the day Saturday.

The problem was discovered before the jet began its take-off, a White House official said.

Another plane took Bush to Charleston, but arrived around 12:00 pmmore than one hour late. The delay forced him to cancel an appearance at a religious service, the official said.

The US president has two identical high-tech jumbo jets to fly around the world under the famed call sign "Air Force One." The iconic plane allows the president to keep constant video links with his aides on the ground.

WAR.WIRE