Faith leaders have called on political leaders to secure a "just, lasting and secure peace" in Iraq and throughout the Middle East.
The Archbishop of Canterbury Dr Rowan Williams said war with Iraq could only be "a limited means to an end".
He was joined by five of Britain's most senior religious leaders from three faiths outside Lambeth Palace as he read out a joint statement.
The comments came as the Muslim Association of Britain urged Muslims to use Friday prayers to pray for peace.
Hundreds of mosques across the UK are expected to take part in the special prayers.
Protests against the war are also expected to take place across Britain throughout the day.
Dr Williams, who has been a vocal opponent of a war against Iraq, said the rights of civilians innocently caught up in the conflict had to be protected.
"We pray that early efforts to achieve a just, lasting and secure peace both in Iraq and throughout the Middle East may follow swiftly in the footsteps of
"We urge those with the power to help make real this vision to remain true,
amid the clamour of conflict, to that noble and vital purpose," he said.
And he called for unity between religions.
"This is a conflict neither about religion nor between religions.
He was joined by the Archbishop of Westminster Cardinal
Cormac Murphy-O'Connor, Free Churches Moderator the Rev David Coffey, Chief Rabbi Dr Jonathan Sacks, the chairman of the Council of Mosques and Imams UK, Dr Zaki Badawi, and co-president of Churches Together In England the Rev Esme
On Thursday Christian and Muslim leaders appealed for unity between faiths amid concern over rising tensions.
Churches Together in Britain and Ireland and The Muslim Council of Britain urged religious communities to come together to pray for peace.
Meanwhile anti-war protesters have taken to the streets across the UK.
The Stop the War Coalition said protests had taken place as far apart as Cornwall and Aberdeen.
In Manchester protesters blocked the roads and a several people were arrested.
An further anti-war demonstration is planned for Saturday in central London,
which is expected to attract tens of thousands of people from across the
Other protests are being planned include a CND rally outside a US air
base in Harrogate and a demonstration outside RAF Fairford in Gloucestershire.