The clergyman had served as the vicar at the Anglican church in Baghdad, Iraq, before being forced to leave following the rise of the Muslim extremist group.
He said he thought there had to be a war to defeat the terrorists who had advanced over large parts of Iraq and Syria killing tens of thousands of Christians.
"It is a terrible thing to say as a priest," he admitted and added that "it really hurts".
"I have tried so hard. I will do anything to save life and bring about tranquillity, and here I am forced by death and destruction to say there should be war."
In an interview with The Independent he said: "We must try and continue to keep the door open. We have to show that there is a willingness to engage. There are good Sunni leaders; they are not all evil like Isis."
The journalist put it to Canon White there was only "one logical conclusion to be drawn", to which he replied: "You are asking me how we can deal radically with Isis. The only answer is to radically destroy them. I don't think we can do it by dropping bombs. We have got to bring about real change. It is a terrible thing to say as a priest."
The vicar, who has been involved in many peace processes across the world including Israel and Nigeria, admitted "you can't negotiate with them".
"I have never said that about another group of people. These are really so different, so extreme, so radical, so evil," he said.
He said before leaving Iraq he invited the leaders of Islamic State to come for dinner with him: "I am a great believer in that. I have asked some of the worst people ever to eat with me".
But they declined saying they would come "but we'll chop your head off".
At one time there were 1.5 million Christians in Iraq but the number has fallen to a quarter of a million since the rise of IS.
"We had Isis on the doorstep of Baghdad last year. I said to my people, 'I will not leave you; don't leave me.' But many did leave me and they went to Nineveh and Mosul. Isis were there too. There was total mayhem." He said.
