"The US intelligence briefings to the Obama campaign have focused on international threats rather than his personal safety. They cover three main dangers: major strikes against US allies - Israel would be the likely top target - that might lead to a dangerous world crisis; attacks on US forces or targets such as embassies; co-operation between unnamed enemy states and terrorist groups to mount the attacks.
"Mr Biden embarrassed his own campaign when an audio tape of his comments to the fundraiser in Seattle were made public. John McCain has regularly referred to the remarks to bolster his argument that Americans should elect him president rather than his inexperienced rival.
"'Mark my words,' Mr Biden said. 'It will not be six months before the world tests Barack Obama like they did John Kennedy. The world is looking. We're about to elect a brilliant 47-year-old senator president of the United States of America. Remember I said it standing here if you don't remember anything else I said. Watch, we're gonna have an international crisis, a generated crisis, to test the mettle of this guy. I can give you at least four or five scenarios from where it might originate.'
"The military source told The Sunday Telegraph: 'Biden had received those briefings and dropped a real clanger when he revealed the conclusions.'"