Pope Leo takes charge of Catholic Church with Vice President Vance looking on

• Pope Leo XIV is the first pontiff from the United States.
• Leo said the church must confront modern challenges while maintaining its traditions, and rejected what he called "religious propaganda" and the misuse of power.
• The pope decried what he called "an economic paradigm that exploits the world's resources and marginalizes the poor."

Pope Leo XIV formally assumed his role as the first American-born leader of the global Catholic Church with a Mass in St. Peter's Square in Rome drawing tens of thousands of people, including dozens of world leaders and European royalty.

As the Mass opened, the Chicago-born pope said in Italian, "Peace be with you and your spirits." He later said the church must confront modern challenges while maintaining its traditions, and rejected what he called "religious propaganda" and the misuse of power.

Leo reached out to conservatives who felt orphaned under his predecessor, vowing to preserve the Catholic Church's heritage and not rule like "an autocrat."

In his Homily, the pope expressed his desire for unity in the Catholic Church and across the world.

"I would like that our first great desire be for a united church, a sign of unity and communion, which becomes a lever for a reconciled world," Leo said. "In this, our time, we still see too much discord, too many wounds caused by hatred, by violence, by prejudice, by the fear of difference, and an economic paradigm that exploits the world's resources and marginalizes the poor."

The new pontiff rode into the square on a popemobile for the first time ahead of his investiture wearing a liturgical garment called the Pallium, made of lambswool.

When the papal Fisherman’s Ring was slipped onto the ring finger of Leo's right hand, he took a moment to glance at the new gold ornament before folding his hands in prayer. The weight of the solemn moment seemed to wash over him.

Vice President JD Vance witnessed the end of one papacy when he visited Pope Francis on Easter Sunday shortly before the pontiff's death. Now, less than a month later, Vance was present for the beginning of another.

It was a moment to celebrate the new leader of 1.4 billion Catholics. The solemn liturgy in St. Peter’s Basilica and Square marked the official beginning of Pope Leo XIV’s pontificate. Vance watched with Secretary of State Marco Rubio.

Other leaders on hand for the grandiose ceremony included Ukrainian President Volodymyr Zelenskyy, Canadian Prime Minister Mark Carney and Australian Prime Minister Anthony Albanese.

Both Second lady Usha Vance and Jeanette Rubio, wife of the secretary of State, entered St. Peter’s Square wearing black lace veils.

U.S. and Peruvian flags for Leo

Well-wishers carried U.S. and Peruvian flags to cheer the first pope from the United States. Born in Chicago, the 69-year-old pontiff spent many years as a missionary in Peru and also has Peruvian citizenship, making him the first pontiff tied to that South American nation.

Delegations from Italy, the United States and Peru received pride of place at the Mass, and Leo later received Vance and Rubio in a long line of visitors, shaking hands with each.

As Leo passed through St. Peter's Square, one person in the crowd shouted out "White Sox, White Sox," referring to the Chicago baseball team at the bottom of the American League standings.

People chanted "Viva il Papa" (Long Live the Pope) and "Papa Leone," his name in Italian.

Robert Prevost, a relative unknown on the world stage who only became a cardinal two years ago, was elected pope on May 8 after a short conclave of cardinals that lasted barely 24 hours.

At his inaugural mass, the pope said now is the time to achieve a unity that does not cancel differences, but “values the personal history of each person and the social and religious culture of every people.”

“Brothers and sisters," he said, "this is the hour for love.”

A papal reset for Trump?

For Trump and his team, the Vance's trip could set the tone for the administration's relationship with the Vatican, which was strained under Francis.

“It was a difference of principles,” said Duke theology professor Peter Casarella.

Trump and Francis repeatedly clashed over immigration.

“A person who only thinks about building walls, wherever they may be, and not about building bridges, is not a Christian,” Francis said at the time.

This year, Francis said of Trump’s mass deportation plan on the eve of his inauguration: “If it is true, it will be a disgrace.” Francis also was a strong advocate for tackling climate change, which Trump has called a “hoax.”

Trump fired back at Francis in 2016, saying: "For a religious leader to question a person's faith is disgraceful." Whether his relationship with Leo will be different remains to be seen, but the new pope seems to share Francis' views.

One day before Leo's inaugural mass, Vance posted photos of himself praying at Francis' tomb. "He was beloved by many Catholics around the world, and I hope you will join me in praying for the repose of his soul," Vance wrote.

Leo said the dignity of migrants should be respected in his first address to world diplomats May 16.

Pope Leo's commitment to social justice

Those who know the new pope say he is committed to social justice and helping migrants. Casarella said when it comes to the church's position on migrants, "the lines are drawn, they can’t change."

Leo shared criticism of Vance and Trump on social media prior to becoming pope.

On April 14, Leo retweeted criticism of Trump and El Salvadoran President Nayib Bukele's response to the controversial deportation of El Salvadoran national Kilmar Abrego Garcia. A decade earlier, Leo shared a 2015 column written by a fellow cardinal with the headline "Why Donald Trump’s anti-immigrant rhetoric is so problematic."

Leo also shared opinion articles critical of Vance's interpretation of Scripture and immigration. "JD Vance is wrong: Jesus doesn't ask us to rank our love for others," one headline posted Feb. 3 reads.

“There’s a long-standing disagreement between Vice President Vance and the papacy about how to interpret Catholic teaching," Casarella said.

Asked about the dynamic between Vance and the new pope, the vice president's office referred to a social media post he put out on May 8 congratulating Leo.

Warm wishes from the White House

"I’m sure millions of American Catholics and other Christians will pray for his successful work leading the Church. May God bless him!" Vance wrote.

Trump also has expressed warm wishes for Leo. The White House brushed off the pope's past social media activity.

"I think it was a surprise to everyone," press secretary Karoline Leavitt said of Leo's social media posts. "But it's a great thing for the United States of America and for the world," she said of the first U.S.-born pope, "and we are praying for him."

Whether Leo continues to weigh in on American politics will be closely watched. A Chicago native, he is the first U.S. pope and there has been intense interest in America in his appointment. He is likely to visit the U.S. in the first few years of his papacy, Casarella said, and could make many trips to the country.

Trump's top Catholics

Vance and Rubio are the two most prominent Catholics in Trump’s administration and his leading surrogates on foreign affairs. They are logical choices to represent Trump at the mass said Joel Goldstein, a St. Louis University professor who studies the vice presidency.

Because both men are considered leading contenders for the 2028 GOP presidential nod, the trip also has "possible political resonance," Goldstein added.

Contributing: Joey Garrison, Francesca Chambers, Reuters