Pope Francis meets with President Trump on the occasion of their private audience at the Vatican on Wednesday.

VATICAN CITY — Setting aside past differences and rude comments, President Trump and Pope Francis put a determinedly positive face on their first meeting Wednesday at the Vatican.

The two global leaders, vastly different in temperament and views of the world, talked seriously and extensively in a 30-minute private meeting about terrorism, the radicalization of young people, immigration and climate change, officials said. Details were not revealed.

But all was upbeat in public, peace the overarching theme.

Francis gave Trump a medal featuring an olive branch.

“We can use peace,” said the president, acknowledging the symbolism.

He gave the pope a custom-bound, first-edition set of Martin Luther King Jr.’s works, an engraved stone from the King Memorial in Washington and a bronze sculpture of a flowering lotus titled “Rising Above.”

“I think you’ll enjoy them. I hope you do,” Trump said.

The pope’s other gifts could be taken as offering a more pointed message, though Francis is known to give them to other visitors.

He gave Trump three bound papal documents that he has written that to some degree define his papacy and priorities. One focuses on the environment, demanding an end to a “structurally perverse” economic system that has turned Earth into an “immense pile of filth.”

President Trump is escorted by a Swiss Guardsman to meet Pope Francis at the Vatican.

He frames climate change as an urgent moral crisis and blames global warming on an unfair, fossil fuel-based industrial model that harms the poor the most.

Trump has expressed skepticism about global warming and possible causes, and he has promised changes to spur more coal and oil production in the U.S.

The president is midway through a grueling nine-day, maiden international journey that has included Middle East stops in the cradles of Islam and Judaism. In Saudi Arabia, he addressed dozens of Arab leaders and urged them to fight extremists at home and isolate Iran, which he depicted as a menace to the region. In Israel, Trump reaffirmed his commitment to strong ties with the longtime U.S. ally and urged Israelis and the Palestinians to work harder toward peace.

He arrived late Wednesday in Brussels.

While Trump received warm welcomes in Riyadh and Jerusalem, the reception could grow cooler now that he’s reached Europe, site of widespread protests after his election. Climate change activists projected the words “Planet Earth First” on the massive dome of St. Peter’s Basilica at the Vatican on Tuesday night, and protests are expected when he attends a NATO meeting in Brussels and a G-7 gathering in Sicily.

As for the Trump-Francis relationship, during the presidential campaign the pope was sharply critical of the candidate Trump’s pledge to build an impenetrable wall on the Mexican border and his declaration that the United States should turn away Muslim immigrants and refugees.

First lady Melania Trump arrives at the San Damaso courtyard for her private audience with Pope Francis.

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

Trump retorted that it was “disgraceful” for the pope to doubt his faith.

There was none of that on Wednesday.

The visit began with a handshake after each man arrived, Trump in a lengthy motorcade, Francis in a Ford Focus.

Their private meeting ended when Francis rang the bell in his study. The pontiff was then introduced to members of Trump’s delegation, including his wife, Melania, his daughter Ivanka and son-in-law Jared Kushner, as well as aides Hope Hicks and Dan Scavino.

Francis had a light moment with the first lady, asking via translator, “What do you give him to eat, potica?” referring to a favorite papal dessert from her native Slovenia.

Pope Francis meets with President Donald Trump at the Vatican.

The first lady laughed and said “Yes.” She and Ivanka covered their heads in a sign of papal respect, a gesture they did not make in Saudi Arabia.

“We had a fantastic meeting,” the president said afterward. He tweeted later that it was the “honor of a lifetime.”

A statement from the Vatican said that “satisfaction was expressed” at their “joint commitment in favor of life” and that there was hoped-for collaboration on health care, assistance to immigrants and protection of Christian communities in the Middle East.

In recent days, Francis and Trump have been in agreement on a need for Muslim leaders to do more against extremists in their own communities. But there are relatively few other areas where their views align.

Trump’s predecessor, Barack Obama, had a private audience with Francis at the Vatican in 2014 that lasted 50 minutes. But the timing Wednesday was tight as Francis had his weekly general audience. The thousands of pilgrims on hand forced Trump’s motorcade to enter Vatican City from a side entrance rather than the grand entrance through St. Peter’s Square.

When Trump left, he told the pope: “Thank you, I won’t forget what you said.”

Trump, the 13th president to visit the Vatican, also toured the Sistine Chapel.

This story has been corrected to reflect that the pope asked about potica, not pizza.