The assault, which killed four American diplomats in the Libyan city of Benghazi was triggered by a mob angered by a film deemed offensive to Islam that Afghanistan has condemned as "inhuman and insulting".

"He has cancelled his trip for the time being. He won't go, he's worried about possible riots over the release of the film," a presidential aide told AFP, requesting anonymity because he was not authorised to speak to the media.

"He prefers to stay at home at such a critical time," the official added.

In Norway, the foreign ministry confirmed that Karzai's arrival had been delayed because the president felt the need to be in Afghanistan after recent events.