Focus of war on terror has been lost, says archbishop

He also criticises the treatment by the US of al-Qaeda suspects held in Cuba.

"It is just possible to deplore civilian casualties and retain moral credibility when an action is clearly focused and its goals are on the way to evident achievement," he writes.

"It is not possible when the strategy appears confused and political leaders talk about a war that may last many years."

Later, a spokesman for Dr Williams said the Archbishop had written the book from a "Christian view".

"The purpose is to examine how we react to the challenges to our faith raised by extreme and murderous violence," the spokesman said.

Dr Williams' comments came as the current Archbishop of Canterbury, Dr George Carey, urged Israelis and Palestinians to return to the negotiating table during a visit to the Middle East.

Dr Carey - spiritual leader of the world's 77 million Anglicans - was speaking on a visit to Yasser Arafat's Ramallah offices, which have been surrounded by Israeli tanks since Friday.

"Religious leaders have a part to play in this," Dr Carey said. "Religion is not only part of the answer, but also part of the problem."

Intellectual

Dr Williams is touted as the leading liberal contender to succeed Dr Carey, and is recognised as an outstanding theologian and intellectual.

Middle East mission: Dr George Carey

He was born in Swansea in 1950 into a Welsh-speaking family from the Swansea Valley.

Educated at Dynevor School, Swansea, he went onto study at Christ's College, Cambridge, and at Christ Church and Wadham Colleges, Oxford.

In 1981, he married Jane Paul, and the couple have two children.

He became Bishop of Monmouth in 1992 and has been the Archbishop of Wales since 2000.

Other potential candidates named for the post include Bishop of London, Richard Chartres, and the Bishop of Rochester, Michael Nazir-Ali.