Pope Leo XIV has warned that artificial intelligence could undermine humanity, cautioning against "losing our humanity amid a paradise of machines invading and conditioning our daily lives" during his opening remarks in France on Friday.

The pontiff delivered the warning in a speech to President Emmanuel Macron and government officials at the Elysee Palace, before repeating the message to diplomats and United Nations employees at the Paris headquarters of UNESCO.

"If we are to avoid losing our humanity amid a paradise of machines invading and conditioning our daily lives, there is an urgent need for education in ethical discernment," Leo said beside Macron.

The pope also addressed the paradox of technological progress. "While 'intelligence' is attributed to computational systems, we struggle to recognise the inalienable dignity of human persons, whose lives are judged according to the criterion of efficiency and, when deemed no longer productive, are rejected and discarded," he said.

At UNESCO, Leo insisted that new technologies must "remain at the service of the human person rather than becoming yet another instrument of domination and injustice." He added: "Every science risks losing its proper meaning when pursued without ethics."

From the start of his pontificate, Leo has identified AI as one of the greatest challenges facing humanity, dedicating his first encyclical to the topic and calling for significant regulation and for developers to work for the common good. He told reporters on the flight to Paris that he was pleased his message was being heard by AI developers and hoped dialogue between tech companies and the Vatican would continue.

Leo also reaffirmed the Vatican's opposition to nuclear weapons, stating that the nuclear deterrence doctrine was "mistaken" as it was fuelling a new arms race. "Peace is not a balance of power; rather, it is built day by day through dialogue and justice," he said.

He criticised world leaders who disrespect the rule of law, without naming individuals. "Instead of respecting the law, those in power invoke it when it serves their interests and disregard it when it restrains them, treating even justice itself as though it were a commodity to be bought and sold," he said.

The pope also raised concerns about scientific progress being turned into "profit-driven ventures promoting genetic manipulation, surrogacy, the trade in human organs or the possibility of arranging one's own death" — remarks made months after France passed legislation granting some adult patients the right to assisted dying.

Leo reminded France of its "deep Christian roots" and called for the French to remember that the right to life is the "indispensable foundation of every other human right." He stressed that "authentic secularity" should not exclude religion "from the public sphere or from education."

Macron welcomed the visit warmly, saying: "You are here with us for an extended visit, giving us your time, and that is moving." He described hosting the pope as a "great honour" and stressed that French secularism "in no way negates religion."

The four-day trip marks the first official papal visit to France in 18 years. Pope Francis had refused to make a full state visit during his 12-year pontificate and declined to attend the inauguration of the rebuilt Notre Dame Cathedral in 2024.

The Vatican estimated that around 300,000 people came out to see the pontiff on Friday. Thousands lined his motorcade route, waving French and Holy See flags, with some braving unseasonable heat for a glimpse of him. In the evening, Leo addressed around 80,000 young people at the Stade de France.

On Saturday, a giant outdoor Mass is planned at the Place de la Concorde, with an altar built on the square and a large area around the Champs-Elysees sealed off by police. More than half a million people are expected to attend. Macron's wife Brigitte and Prime Minister Sebastien Lecornu will be present, along with several candidates for next year's presidential election, including Marine Le Pen, Edouard Philippe, Gabriel Attal and Bruno Retailleau. Macron himself will not attend any of the papal Masses, largely to avoid breaching France's strict separation of church and state.

On Sunday, 150,000 people have signed up to attend Mass at the Pyrenean sanctuary of Lourdes, where Leo will also privately meet victims of clerical sexual abuse. France's Catholic bishops' conference has agreed to provide compensation after a 2021 report estimated that 330,000 children were sexually abused over 70 years by priests or other church-related figures in France.

On Monday, Leo will travel to Metz in northeast France, where he will pay tribute to Robert Schuman, a founding father of the European Union and a candidate for beatification, and deliver a speech on European peace as Russia's full-scale invasion of Ukraine continues into its fifth year.

Leo, who was born in Chicago in 1955 as Robert Prevost, has French ancestry. His paternal grandmother was born in Le Havre, Normandy, in 1894.