Welby: 'Action should only be taken when there is no other alternative'
29 August 2013 Last updated at 19:13 BST
A House of Lords debate on intervention in Syria is under way.
The Archbishop of Canterbury, Justin Welby, said: "The step of opening fire is one that must only be taken when there is no possible alternative."
He warned the consequences would be "totally out of hands once it has started".