The Archbishop of Canterbury has told ITV News Christians in the Middle East are calling for a "step-change" in response to violence led by Islamic State militants.
He said Britain had to be "cautious but immensely determined" in its approach but said on some occasions "military and intelligence experts can see that they can make a difference".
Archbishop Welby added that others in the Church had told him the region had not seen such levels of violence since the invasion of Genghis Khan in the 13th Century.
They were all saying that this is a new event - this is a great change, a step-change in what is happening and needs a step-change in our response.
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.