Pope Leo XIV greets the crowd from the popemobile before a Holy mass for the beginning of his pontificate, in St Peter's square in The Vatican on May 18, 2025. Stefano Rellandini, AFP

VATICAN CITY, Holy See (2nd UPDATE) -- Pope Leo XIV set the tone for his papacy with a call to stop exploiting nature and marginalising the poor at his inaugural mass Sunday attended by dignitaries including Ukraine's Volodymyr Zelensky and US Vice President JD Vance.

Ten days after he became the first US head of the world's 1.4 billion Catholics, some 200,000 people gathered to see his inaugural mass in St Peter's Square, according to the Vatican.

Before it started, the Chicago-born Robert Francis Prevost delighted the crowds by taking to the popemobile for the first time, smiling, waving and blessing those he passed.

In his homily, the soft-spoken 69-year-old returned to the themes of peace, reconciliation and social justice that have marked his first few days as pope.

"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.

In a prayer afterwards, he noted the ongoing efforts to end the war in Ukraine, before holding a private audience with Zelensky and his wife.

"The martyred Ukraine is waiting for negotiations for a just and lasting peace to finally happen," Leo said.

After two decades spent as missionary in Peru, the new pope -- who was only made a cardinal in 2023 -- is unknown to many Catholics.

But many of those gathered in St Peter's Square said they liked what they had heard so far.

Maria Grazia La Barbera, 56, a pilgrim from Palermo in Sicily, said Leo was "the right person at the right time" to lead the Church.

"He will certainly do what he promised: knocking down walls and building bridges," she said.

READ: Pope Leo XIV to celebrate inaugural mass

- Vance 'very proud' -

Leo's elevation has sparked huge enthusiasm in the United States, which was represented on Sunday by Vance, who converted to Catholicism in 2019.

Vance met with the late Pope Francis the day before he died last month, and queued up to shake Leo's hand on Sunday along with the other dignitaries.

Before becoming pope, Leo reposted on his personal X account criticism of US President Donald Trump's administration over its approach to migration and also pilloried Vance.

But Vance insisted Sunday that the United States was "very proud of him".

"Certainly our prayers go with him as he starts this very important work," Vance said at a meeting with EU chief Ursula von der Leyen and Italian Prime Minister Giorgia Meloni.

There is some consternation outside the United States that a country with an already outsized political and military role in the world now boasts one its foremost spiritual leaders.

"There is going to be extra weight because he is American," said Sophia Tripp, a 20-year-old student visiting from Leo's hometown of Chicago.

"I think there's going to be a lot of extra eyes, and maybe criticisms."

She hoped he would "bring people together", she said. "We are all human, and we should just all be loving to one another."

READ: Leo XIV gets down to business on first full week as pope

READ: Pope offers to mediate between world leaders to end wars

- 'Fear and trembling' -

Security was tight for the event, which included politicians from Germany to Peru -- where the pope holds citizenship -- the Gulf and Canada, as well as faith leaders and European royals.

Also lining up to greet the new pontiff inside St Peter's Basilica after the mass was Leo's older brother Louis, and the two men shared a hug.

Succeeding the charismatic but impulsive Francis, Leo took over a Church still battling the fallout of the clerical child abuse scandal, and trying to adapt to the modern world.

He acknowledged on Sunday some trepidation in his new role.

"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," he said.

In his homily he warned against "closing ourselves off in our small groups".

"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.

At the mass, Leo received the pontifical emblems -- the pallium, a strip of cloth worn around the neck, and the fisherman's ring, which is forged anew for each pope.

He will wear the ring on his finger until he dies, when it will be destroyed.

© Agence France-Presse

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