Tight security at the US embassy in Dublin reached new heights when it left the president's car in a jam.
The low-riding limousine got stuck on a steep ramp at the entrance to the American diplomatic mission as Mr Obama and first lady Michelle were leaving.
The armour-plated Cadillac, nicknamed "The Beast", came to a halt as the bomb-proof under-carriage snagged on the riser.
The White House press secretary refused to comment, insisting the embarrassing mishap was being dealt with by the secret service.
It was not clear if the president and Mrs Obama were in the car or if it was a decoy leaving the embassy grounds.
The president's cavalcade always contains two identical limousines. It is said some of his closest security staff do not know which car he will be in.
Security staff eager to avoid footage of the blunder being beamed around the world quickly called in a blacked-out minibus to cover the gates and sight of the limousine.
A double-decker Dublin bus was later driven up as a bigger shield.
It was the only transport scare in the whistle-stop tour, despite volcanic ash threatening to ground the president's plane Air Force One and concerns over the use of helicopter Marine One in gale-force winds and driving rain.
The Cadillac has its own oxygen supply in case of chemical attack and is fitted with state-of-the-art communication technology.