By Alex Kirby
BBC News Online
Most of the Christian churches have a long tradition of facing both ways over war.
War is always a failure, say UK archbishops
They are not pacifist, accepting there can be a just war, if it meets certain conditions.
This time, though, there is vehement opposition to any attack on Iraq, with few dissenters - a surprisingly united front.
The churches' hopes of preventing war seem slight, but they may still wield a significant indirect influence.
The list of churches urging the world's leaders to resolve the Iraqi crisis without force is long.
Pope John-Paul II has said the use of military force must be the "very last option".
Iraqis are facing an enormous human disaster if there is a war. We are on the verge of opening a Pandora's box
John McCullough, Church World Service
He said: "War is never just another means that one can choose to employ for settling differences between nations."
The World Council of Churches (WCC) represents about 400 million Christians, mainly from Protestant and Orthodox churches.
Into the unknown
In October 2002 it told members of the United Nations Security Council it "deplored the fact that the most powerful nations of this world continue to regard war as an acceptable instrument of foreign policy, in violation of both the UN Charter and Christian teachings".
In his letter the WCC general secretary, Dr Konrad Raiser, said: "The people of Iraq have suffered enough under a sanctions regime since 1991.
Plenty of cardinals, no divisions
"Inflicting further punishment on innocent civilians is not morally acceptable to anyone."
John McCullough is executive director of Church World Service, a division of the US National Council of Churches.
On returning from a five-day trip to Iraq, he said: "Iraqis are facing an enormous human disaster if there is a war. We are on the verge of opening a Pandora's box."
The leaders of the UK's Catholic and Anglican churches, Cardinal Cormac Murphy-O'Connor and the archbishop of Canterbury, Dr Rowan Williams, have added their voices to the growing chorus.
In a joint statement, they say war inevitably brings "a sense of failure", and call for United Nations weapons inspections to be given more time.
But a nagging thought in the mind of every church leader, and every Christian, must be the question Stalin once asked: "How many divisions has the Pope?"
Few churches wield much overt political power these days, and certainly not enough to deflect politicians bent on a course of action.
So it looks unlikely that even this rare display of Christian unity will be enough to halt the war in its tracks.
Iraq has suffered enough, says WCC
But churches do still have influence: many individual Christians will conclude that this time their gospel does direct them unambiguously to oppose war.
The state's ultimate sanction is armed force, and the churches know that members of the military are often Christians.
That is one reason why mainstream Christianity has always found it impossible to settle for pacifism - from its early days it has been closely identified with the state.
In most of the wars of the last 50 years that have involved the Western democracies, the churches have had to minister to Christians in uniform and on the barricades.
They still do. But modern democratic armies do not exist outside society - they are part of it.
The armed forces seldom want to wage war unless they feel they have the moral support of people back home.
Christians, with many other people, are a reminder to the forces in the Gulf that this time they may have to fight without much support.