US President Trump and first lady Melania talk with Pope Francis

Pope Francis urged Donald Trump to use his U.S. presidency to promote peace around the world as the two leaders swapped sparring for smiles in their first face-to-face meeting, at the Vatican yesterday.

Trump's audience with the 80-year-old pontiff, a keenly-anticipated highlight of his first overseas tour, lasted just under half an hour and concluded with both men smiling.

"He is something," the president later said of his host. "We had a fantastic meeting." 

The Vatican described the discussions as "cordial" and stressed the two men's joint opposition to abortion and shared concern for persecuted Christians in the Middle East.

There was no mention from either side of the two men's profound differences on climate change, migration, the death penalty and other issues.

Trump told his host as he left: "Thank you. Thank you. I won't forget what you said."

The pope had presented Trump with a medallion engraved with an olive tree, the international symbol of peace.

"I give it to you so you can be an instrument of peace," he said in Spanish. "We can use peace," Trump replied.

In a lighter moment, Francis referred to Trump's imposing bulk by asking his wife Melania, "What do you feed him on? Potica?" - a reference to a calorie-laden cake from Slovenia, Melania's country of birth.

Trump presented the pope with several gifts, including a collection of first editions by Martin Luther King and a bronze sculpture.

Francis gave Trump copies of the three major texts he has published as pope, including one on the environment which urges the industrialized world to curb carbon emissions or risk catastrophic consequences for the planet.

Trump, who has threatened to ignore the Paris...