VATICAN CITY (AP) 鈥 Pope Leo XIV, history鈥檚 first American pope, vowed Sunday to work for unity so that the Catholic Church becomes a symbol of peace in the world, offering a message of communion during an inaugural Mass in St. Peter鈥檚 Square before an estimated 200,000 pilgrims, presidents, patriarchs and princes.

Leo officially opened his pontificate by taking his first popemobile tour through the piazza, a rite of passage that has become synonymous with the papacy鈥檚 global reach and mediatic draw. smiled and waved from the back of the truck, and stopped to bless some babies in the crowd.

During the Mass, Leo appeared to choke up when the two potent symbols of the papacy were placed on him 鈥 the lambswool stole over his shoulders and the fisherman鈥檚 ring on his finger 鈥 as if the weight of responsibility of leading the 1.4-billion strong church had just sunk in.

He turned his hand to look at the ring and seal and then clasped his hands in front of him in prayer.

U.S. Vice President JD Vance, one of the last foreign officials to , led the U.S. delegation honoring the Chicago-born Leo. Vance paid his respects at the Argentine pope's tomb upon arriving in Rome late Saturday.

The theme of Leo's papacy

In his homily, Leo said he wanted to be a servant to the faithful through the two dimensions of the papacy, love and unity, so that the church could be a force for peace in the world.

鈥淚 would like that our first great desire be for a united church, a sign of unity and communion, which becomes a leaven for a reconciled world,鈥 he said. 鈥淚n this our time, we still see too much discord, too many wounds caused by hatred, violence, prejudice, the fear of difference, and an economic paradigm that exploits the Earth鈥檚 resources and marginalises the poorest.鈥

His call for unity was significant, given the polarization in the Catholic Church in the United States and beyond.

Francis鈥 radical 12-year pontificate, which emphasized care for the poor and marginalized and disdain for the capitalist economic system, often Leo鈥檚 May 8 election, after a remarkably quick 24-hour conclave, appears to have pleased conservative Catholics who seem to appreciate his more disciplined, traditional style and Augustinian background, emphasizing core truths of Catholic doctrine.

Leo drove that message home further by wearing the formal red cape of the papacy, or mozzetta, to receive Vance and official government delegations after the Mass. Francis had eschewed many of the formalities of the papacy as part of his simple style, but Leo's return to the traditional garb has pleased conservatives and traditionalists who cheered when he came out of the loggia on May 8 wearing the red cape.

Leo did though break protocol when he gave his older brother, Louis Prevost, a self-described political 鈥淢AGA-type,鈥 a bear hug in the basilica when he and his wife came up to greet the pope.

鈥淟et us build a church founded on God鈥檚 love, a sign of unity, a missionary church that opens its arms to the world, proclaims the word, allows itself to be made restless by history, and becomes a leaven of harmony for humanity,鈥 Leo said, referencing some of the themes of Francis' pontificate as well.

Tight security and protocol

Strict diplomatic protocol dictated the seating arrangements at the inaugural Mass, with both the United States and thanks to Leo鈥檚 dual citizenship. Vance, a Catholic convert who over the Trump administration鈥檚 was joined by U.S. Secretary of State Marco Rubio, who arrived in Rome ahead of time to try to

Peruvian President Dina Boluarte was one of around a dozen heads of state who attended, as well as Ukrainian President Volodymyr Zelenskyy. Russia had planned to send its culture minister but was represented by its ambassador, reports said.

Diplomatic protocol also dictated the dress code: While most wore black, the handful of Catholic queens and princesses 鈥 Letizia of Spain and Charlene of Monaco among others 鈥 wore white in a special privilege allowed them. Three dozen of the world鈥檚 other Christian churches sent their own delegations, the Jewish community had a 13-member delegation, half of them rabbis. Other representatives headed Buddhist, Muslim, Zoroastrian, Hindu, Sikh and Jain delegations.

Security was tight, as it was for which drew an estimated 250,000 people. The Vatican said 200,000 were on hand Sunday in the piazza and surrounding streets, parks and piazzas, where giant television screens and portable toilets were set up.

At the end of the Mass, Leo expressed hope for negotiations to bring a and offered prayers for 鈥 children, families and elderly who are 鈥渞educed to starvation,鈥 he said. Leo made no mention of hostages taken by Hamas from southern Israel on Oct. 7, 2023, as Francis usually did when praying for Gaza.

Americans are rejoicing

Susan Hanssen, a professor who was born in Chicago and just arrived in Rome to teach, said she thought Leo鈥檚 homily of unity would resonate in the U.S. and beyond. 鈥淚 think he will inspire,鈥 she said after Mass. 鈥淲hat I particularly loved was the phrasing, unity within the doctrine of the faith, and then in love.鈥

U.S. seminarian Ethan Menning, 21, from Omaha, Nebraska, wrapped himself in an American flag, purchased at a truck stop in Iowa, to celebrate.

鈥淩ome always felt like home for a Catholic, but now coming here and seeing one of our own on the throne of Peter ... it almost makes Jesus himself more accessible,鈥 he said.

The two symbols of the papacy handed to Leo were the pallium stole, and the . The pallium, draped across his shoulders, symbolizes the pastor carrying his flock as the pope carries the faithful. The ring, which becomes Leo鈥檚 official seal, harks back to Jesus鈥 call to the apostle Peter to cast his fishing nets.

The other symbolically important moment of the Mass was the representational rite of obedience to Leo: Whereas in the past all cardinals would vow obedience to the new pope, more recent papal installations involve representatives of cardinals, bishops, priests, deacons, nuns, married couples and young people participating in the rite.

Gregory and Susan Hudak, who lived for 40 years in the Chicago area, found themselves in Rome after booking a trip in February, with just a faint hope of perhaps glimpsing the pope. Seeing the popemobile pass by in front of them, with the Chicago-born Leo on board, was even better than watching Michael Jordan play, said Gary Hudak, a former altar boy wearing a Chicago Bears hat.

鈥淥riginally, the only hope I had coming here was to see the inside of the Sistine Chapel," he said. "Seeing the pope was not scheduled, it was a long shot hope. And this was a treasure, simple as that.鈥

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Associated Press writers Giovanna dell'Orto and David Biller, and AP visual journalist Isaia Monteleone contributed to this report.

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Associated Press religion coverage receives support through the AP鈥檚 with The Conversation US, with funding from Lilly Endowment Inc. The AP is solely responsible for this content.

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