The Prince's remarks came in a personal letter to Archbishop Louis Sako, the Patriarch of Babylon of the Chaldeans, the head of the Caldean Catholic Church which stretches across Iraq and Syria and other parts of the region, accompanying a donation through the charity Aid to the Church in Need.
"You can have no idea how heartbroken I am to hear of the truly unbearable and barbaric persecution being suffered not only by the Christians in Iraq, but also by some of their neighbours of other faiths alongside whom you have lived for hundreds of years," he said.
He added: "Although words seem hopelessly inadequate at such an unimaginable time of suffering, I did just want to offer, through you, my special prayers and profound sympathy to all the members of the Caldean Catholic Church in Iraq."
The Prince underlined the word "profound" in black ink, adding: "It is my fervent hope and prayer that the leadership and actions of people of goodwill such as yourself and your brothers and sisters will help to overcome the diabolic evil that has wrought this terrible suffering and allow peace to return to the cradle of civilisation."
He signed it by hand: "Yours most sincerely, Charles."
Speaking at Lambeth Palace, Archbishop Welby and the Middle Eastern church leaders said they were praying for the family and friends of Steven Sotloff. The Archbishop added that no-one should underestimate the tensions faced by David Cameron and other heads of government.
"I think it took the barbarism of the Jihadist militants to wake us up," he said.
"As someone in the meeting earlier said very eloquently that this is a new thing; that there has not been treatment of Christians in this region in this way since the invasion of Genghis Khan in 1260.
"This is a new phenomenon and I think we always find it hard to believe that such horrors can happen."
But he stopped short of backing military action saying that the church in the Middle East was divided over whether it would do more harm than good.
