Pope Leo XIV, the first American to lead the Roman Catholic Church, used his inaugural Mass on Sunday to condemn economic systems that exploit the Earth and marginalize the poor, setting a clear tone for his papacy before tens of thousands of pilgrims and global dignitaries.

"In 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's resources and marginalises the poorest," he said during his homily in St. Peter’s Square.

The 69-year-old Chicago-born pontiff, formerly Cardinal Robert Francis Prevost, made his debut tour in the popemobile, waving and blessing a crowd that included U.S. Vice President J.D. Vance, Ukrainian President Volodymyr Zelensky, and other world leaders.

Leo XIV, a former missionary in Peru, also urged Catholics to resist isolation and embrace diversity. "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.

His ascension to the papacy on May 8 follows the death of Pope Francis and comes amid continued fallout from clerical abuse scandals and growing calls for Church reform.

Leo’s remarks highlighted his focus on peace and social justice — themes that have already won him support among some faithful. "He has already entered my heart," said Inacia Lisboa, a pilgrim from Cape Verde. "We need peace in the world — so much."

Security was tight in Rome, with thousands of officers, snipers, and anti-drone units deployed. Among attendees were leaders from Germany, Italy, Peru, Canada, Israel, Colombia, the EU, and several European monarchies.

Leo’s U.S. nationality has sparked excitement at home and curiosity abroad. “There’s going to be a lot of extra eyes, and maybe criticisms,” said Sophia Tripp, 20, visiting from Chicago. “But we are all human, and we should just all be loving to one another.”

Before Mass, the new pope visited the tomb of Saint Peter and received the traditional papal emblems, including the pallium and the fisherman’s ring.

"I was chosen, without any merit of my own, and now, with fear and trembling, I come to you as a brother who desires to be the servant of your faith and your joy," Leo said.