The Archbishop of Canterbury today endorsed the possible use of armed force in the war against religious "extremism".

He said the world is engaged in "a great struggle", noting that it has been described recently as a "Third World War". He added: "Let me be clear, it is not a war against Islam."

He said: "It is theological and ideological. There will be aspects that may involve the use of armed force in a quasi-policing form. We will differ over when that is right and wrong. Yet at the heart of this conflict, for the first time in centuries in Western Europe, is theology."

Archbishop Justin Welby said religious extremism is global. The world faces an ideological or theological struggle.

"It is a war against extremism and the fundamentalism that prefers to defy God himself rather than to live in holiness with those whom we are called to love. We are called to love God, one another, our neighbour, our enemy."

The Archbishop was addressing the newly-elected General Synod of the Church of England and acknowledged that the meeting was taking place "in the shadow of Paris."

He said: "Those who are pepole of faith have a challenge, and a task. The challenge is to be like Jesus Christ, the Prince of Peace. The task is to overwhelm extremism not by other extremes but with hope and love."

The war must be won if faith of any kind is to have a reputation in a public mind, the Archbishop said.

He also urged the church to cease fighting its own internal wars, allowing that there will always be divergence of opinions deeply held, yet maintaining that the unity found in Jesus must overcome them.

He said that the Westminster model of "equivalence and exchange", where decisions in the Synod are regarded as a zero-sum game, "is not the logic of the body of Christ."

He suggested instead that "If any lose, we all lose. If any win, we all win. My first hope is the counter to that fear, the extreme opposite."