Pope Benedict XVI's top official for justice issues said on Tuesday it was unacceptable to resort to torture in hopes of extracting information that might thwart a terrorist attack.
The pope himself referred to fundamentalism in the Vatican's annual review of conflicts in the world.
"Religious fanaticism, today often labeled fundamentalism, can inspire and encourage terrorist thinking and activity," Benedict warned.
His message, which was issued for the approaching new year, also lamented that international diplomacy aimed at eliminating nuclear menace had become "bogged down."
Benedict paid tribute to his predecessor, Pope John Paul II, who vigorously opposed the war in Iraq, and said the Church would continue "serving the cause of peace."
In analyzing causes of terrorism, "consideration should be given not only to its political and social causes, but also to its deeper cultural, religious and ideological motivations," the pontiff said.
At a news conference about the peace message, Cardinal Renato Martino, head of the Vatican's pontifical council on peace and justice, was asked if torture could be a legitimate tool to gain information that might prevent terror attacks.
The prelate replied that there was no justification for the use of torture, which is the "humiliation of the human person, whoever he is."
"The Church does not allow torture as a means to extract the truth," Martino said. Terror suspects "sometimes say what the torturers want to hear ... There are other ways to obtain the truth."
Benedict noted that the Holy See had called for the prompt implementation of international humanitarian conventions dealing with the effects of wars.
"Respect for that law must be considered binding on all peoples," the pontiff said.
That prompted a reporter to ask Martino if the pope was concerned about allegations of secret CIA prisons in Europe.
The pope "is not condemning anybody, but is inviting them to observe the Geneva Convention" on the treatment of prisoners of war, said Martino, who used to be the Vatican's ambassador to the UN.
Benedict urged reforms that would make the UN "a more efficient instrument" in promoting peace and justice.
The pontiff said he was dismayed about "a continuing growth in military expenditures and the flourishing arms trade, while the political and juridical process established by the international community for promoting disarmament is bogged down in general indifference."
Negotiations are stalled between Iran and the EU aimed at making Tehran permanently freeze nuclear enrichment. That process can produce material for use in warheads or fuel for nuclear plants to generate electricity.
And tensions have marked much of the diplomacy to persuade North Korea to give up its nuclear programs in exchange for aid and security guarantees.
"The truth of peace requires that all -- whether those governments which openly or secretly possess nuclear arms, or those planning to acquire them -- agree to change their course by clear and firm decisions, and strive for a progressive and concerted nuclear disarmament," Benedict said.