The ageing pontiff rebuffed attempts by the Bush Administration to persuade him that impending military action against Baghdad amounted to a Christian “just war”.

Today he will dispatch a personal peace envoy to Baghdad to urge President Saddam Hussein to co-operate fully with United Nations weapons inspectors.

At the end of the week he will meet Tariq Aziz, Iraq’s Deputy Prime Minister and an Arab Christian, in Rome, and will also meet Kofi Annan, the UN Secretary-General. Diplomats said that Mr Aziz might remain in Rome to meet Mr Annan under the auspices of the Vatican.

Looking and sounding like a man rejuvenated by the urgent need to avert the imminent conflict, the Pope, 82, also gave his backing to the new Franco-German plan to resolve the Iraq crisis through beefed-up weapons inspections and the deployment of UN troops. The plan was disclosed to the Pope on Friday by Joschka Fischer, the German Foreign Minister. Diplomats said that the Pope had been “the first world figure to be told of the plan”.

Yesterday the Pope made a dramatic and impassioned appeal for world prayers, declaring that only God could stop the conflict now. “At this hour of international worry we all feel the need to look to God and beg him to grant us the great gift of peace,” he told pilgrims and visitors in St Peter’s Square. Only “an act from on high” could offer hope of altering what appeared to be a bleak future.

The Pope is sending Cardinal Roger Etchegaray, his diplomatic troubleshooter, to Baghdad. Cardinal Etchegaray, a French Basque, has undertaken sensitive diplomatic missions for the Pope in the past. Last year he helped to negotiate an end to the siege of the Church of the Nativity in Bethlehem, where Palestinian gunmen had taken refuge.

At the weekend the Pope said that efforts to stave off war must be multiplied. “One cannot do nothing in the face of terrorist attacks, but equally one cannot be idle in the face of the threats now on the horizon,” he said. “War is not inevitable.”

The case for a “just war” was made at the weekend by Michael Novak, a conservative Roman Catholic theologian and a close ally of President Bush, in talks with senior Vatican officials, including Archbishop Jean-Louis Tauran, the Pope’s Foreign Secretary.

Under the principles of “just war”, as formulated by St Augustine of Hippo and later by St Thomas Aquinas, war can be waged only as a last resort and by a “legitimate authority”. It must be fought with “right intentions”, for example in self-defence or to redress a wrong, and with a reasonable chance of success to avoid excessive death and injury. The theory of just war also holds that civilian casualties must be avoided, that the means used must be proportionate and that the ultimate goal should be to establish a peace “preferable to what would have prevailed if the war had not been fought”.

Mr Novak, who today will address a conference in Rome on just war organised by James Nicholson, the US Ambassador to the Holy See, insisted that war against Iraq amounted to self-defence. He told Archbishop Tauran that Saddam was using Iraqi scientists “to breed huge destruction in the US and Europe”. He said that those who opposed war would have a lot on their consciences if the United States failed to act and Americans were later killed by Saddam’s weapons. The Catholic catechism also justified the use of force provided that it was sanctioned by those responsible for the common good, Mr Novak said.

But the Archbishop, speaking for the Pope, said that US arguments were insufficient and that there was no imminent threat from Baghdad that could justify a war.

Civiltà Cattolica (Catholic Civilisation), a Jesuit journal that reflects Vatican views, said that “the Islamic masses, which already harbour a deep hatred of the West, will see it as an act of war against Islam”. The journal said that the real US motive was economic and that the concept of “preventive war” was highly dangerous. “If every country which feels threatened attacks first, there will be war without end on the entire planet,” it said.

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