The Vatican has forcefully restated the Catholic Church's position that preventive wars are permissible only with "clear proof" of an imminent attack.
The position on war and peace, on legitimate defence and aggression was found in the new Compendium of the Social octrine of the Church, a 330-page tome published by the Vatican's Pontifical Council for Justice and Peace.
While the book is mainly a compilation of known Church teachings on a host of social issues, its chapter called "The Promotion of Peace," is one of the most topical because of the war in Iraq and the November 2nd US presidential elections.
It made no specific reference to Iraq, but defended the Charter of the United Nations, which prohibits a recourse to conflict to resolve disputes except in cases of legitimate defence and when backed by the UN Security Council.
"Therefore, engaging in a preventive war without clear proof that an attack is imminent cannot fail to raise serious moral and juridical questions," it said.
The Vatican strongly opposed the US-led invasion of Iraq and the Pope sent senior cardinals to US President George Bush and former Iraqi leader Saddam Hussein to try to avert it.
The Vatican envoy the Pope dispatched to Washington before the invasion, Cardinal Pio Laghi, emerged from his meeting with Mr Bush and said any war without UN backing would be "illegal". The new compendium appeared to back up that position.
"International legitimacy for the use of armed force ... can only be given by the decision of a competent body that identifies specific situations as threats to peace...," it said.