The global impact of the latest beheading of a western hostage is starting to take shape as leaders arrive in Wales for a summit beginning tomorrow.
David Cameron is refusing to rule out British air strikes against Islamic State, while US politicians have been increasingly vocal in their threats against the radical group.
ITV News International Affairs Editor Rageh Omaar reports:
I've been told at the Nato summit that the intelligence services know exactly who 'Jihadi John' is - or at least are 99.9% certain.
The British aid worker being held by Islamic State is David Haines, a 44-year-old father-of-two from Perth, Scotland.
In a video statement which claims to record his final words US hostage and journalist Steven Sotloff blames US foreign policy for his death.