Washington's plans for oil-rich Libya have been thrown into disarray after the assassination of its ambassador and several other embassy staff.
Their deaths yesterday were revealed by Libyan officials today and later confirmed by the US.
Ambassador Christopher Stevens was reported to have been trying to flee the consulate building in the eastern city of Benghazi when his car was apparently ambushed by unknown attackers.
They launched a rocket attack that left the ambassador and three other US embassy staff dead.
Washington initially remained tight-lipped on the full scale of the blow to its interests, only doing so hours after confirming the death of one consulate employee when its main office in Libya's second city was stormed, ransacked and burned to the ground.
The assailants were said to be Islamists outraged at a film linked to rabid anti-Muslim US Pastor Terry Jones called Mohammed, Prophet of the Muslims. The extremist Jewish US film-maker Sam Bacile went into hiding today.
Hours before the Libya attack an angry mob in Cairo had stormed the walls of the US embassy there before tearing down the US flag and hoisting a black Islamic flag in its place.
Both incidents took place on the 11th anniversary of a string of al-Qaida terrorist attacks in the US on September 11 2001.
US President Barack Obama condemned the deadly attack in Libya as "outrageous" and ordered higher levels of security at diplomatic sites across the world.
"While the United States rejects efforts to denigrate the religious beliefs of others, we must all unequivocally oppose the kind of senseless violence that took the lives of these public servants," he said.
However the grim irony of the way in which Mr Stevens reportedly died will not be lost on supporters of the ex-dictator whose former Western allies turned against him to support an Islamist-dominated revolution last year.
After months of aerial bombardment by Nato warplanes and special forces support on the ground in which thousands died, Muammar Gaddafi was finally killed by a mob as he tried to flee his last hiding place by car.