Leo, the first US pope, did not name specific leaders in the message released before the Catholic Church's World Day of Peace, celebrated on January 1, but called on religious believers to resist any such uses of faith.
"Unfortunately, it has become increasingly common to drag the language of faith into political battles, to bless nationalism, and to justify violence and armed struggle in the name of religion," the Pope said.
"Believers must actively refute, above all by the witness of their lives, these forms of blasphemy that profane the holy name of God."
Leo also warned against the use of artificial intelligence in warfare in the four-page message, issued annually by the leader of the 1.4 billion-member church.
"There is ... a growing tendency among political and military leaders to shirk responsibility, as decisions about life and death are increasingly 'delegated' to machines," he said.
"This marks an unprecedented and destructive betrayal of the legal and philosophical principles of humanism that underlie and safeguard every civilisation."
Leo, elected by the world's cardinals in May to succeed the late Pope Francis, has spoken several times in his first year about the challenges posed by AI.
He also condemned violence in the name of religion on his first overseas trip as pontiff, telling Christian leaders across the Middle East during a trip to Turkey in November they must "strongly reject the use of religion for justifying war, violence, or any form of fundamentalism".
In the new message, the Pope also lamented a global increase in military expenditures, citing figures from the Stockholm International Peace Research Institute that worldwide military outlays increased almost 10 per cent in 2024, reaching a total of $US2.7 trillion ($A4.1 trillion).
Leo warned against a "confrontational logic (that) now dominates global politics, deepening instability and unpredictability day by day".
