Pope Leo XIV calls for unity and 'missionary spirit' during inaugural mass

LONDON and ROME -- Pope Leo XIV spoke on Sunday of the remarkable times during which he's been elevated to the papacy, saying in his first homily as pontiff that he will rise to the task "with fear and trembling," while still seeking to serve all with "faith and joy."

That homily was delivered during the American pope's inaugural mass, called the Holy Mass for the Beginning of the Pontificate, in St. Peter's Basilica at the Vatican. An open-topped popemobile had driven Leo on Sunday morning through St. Peter's Square, where about 100,000 people had gathered to catch a glimpse of him, according to the Vatican's press office.

The pope said during his homily that there's "too much discord, too many wounds caused by hatred, violence, prejudice, the fear of difference, and the economic paradigm that exploits the Earth's resources and marginalizes the poorest."

He called for the world's 1.4 billion Catholics to embrace a "missionary spirit," rather than closing themselves off "in our small groups." He called for the faithful to discard feelings of being "superior to the world."

"We are called to offer God's love to everyone, in order to achieve that unity which does not cancel out differences but values the personal history of each person and the social and religious culture of every people," he said.

Attendees at the mass, which marks the official beginning of Leo's papacy, included Vice President JD Vance and Secretary of State Marco Rubio, along with other political figures and religious dignitaries.

Canadian Prime Minister Mark Carney and Australian Prime Minster Anthony Albanese were in attendance. And representatives of the Ecumenical, Jewish, Muslim, Hindu, Buddhist, Sikh, Zoroastrian and Jain churches were there, the Vatican's Holy See press office said.

Vance and Ukrainian President Volodymyr Zelenskyy greeted each other and shook hands prior to the mass. The Vatican said the pope was expected to hold a private audience with Zelenskyy on Sunday. The pope met with Peruvian President Dina Boluarte prior to the mass, the Vatican said.

Leo, who was formerly Cardinal Robert Prevost, is a 69-year-old native of Chicago, Illinois. Elected on May 8, he's the first American to lead the church.

During the ceremony, Filipino Cardinal Luis Antonio Tagle presented Leo with his Ring of the Fisherman. Leo will wear that ring, which celebrates Saint Peter, who was the first pope, throughout his papacy.

Pope Francis, Leo's predecessor, died on April 21, after he was discharged from a weeks-long hospital stay. The newly installed pontiff also paid tribute to him, saying on Sunday his death "filled our hears with sadness."

And he gave some insight into the papal conclave that saw him elected earlier this month.

As 133 cardinals gathered in the Sistine Chapel, they "could feel the working of the Holy Spirit," Leo told the crowd on Sunday, adding that the spirit "was able to bring us into harmony, like musical instruments, so that our heartstrings could vibrate in a single melody."

"I was chosen, without any merit of my own, and now, with fear and trembling, I come to you as a brother," he said, "who desires to be the servant of your faith and your joy, walking with you on the path of God's love, for he wants us all to be united in one family."

By the time the Regina Caeli Prayer was to be read, toward the end of the mass, the crowds in the square and those lining the surrounding streets had swelled to some 200,000 people, according to the Vatican's press office.

Leo, in remarks before the prayer, offered a warm welcome to those thousands, thanking many for making pilgrimages from far afield. He said he had during mass "strongly felt the spiritual presence of Pope Francis accompanying us from heaven." And he closed by urging the faithful to "support and comfort for those who suffer."

"In the joy of faith and communion, we cannot forget our brothers and sisters who are suffering because of war," he said. "In Gaza, the surviving children, families and elderly are reduced to starvation. In Myanmar, new hostilities have cut short innocent young lives. Finally, war-torn Ukraine awaits negotiations for a just and lasting peace."

ABC News' Megan Forrester and Clark Bentson contributed to this report.