President Trump tweeted Wednesday that meeting Pope Francis was "the honor of a lifetime."

Trump met with the pope in a private study at the Vatican for 30 minutes on Wednesday. The meeting was part of Trump's first foreign trip as president. Trump was joined by his wife Melania, his daughter Ivanka, her husband and senior adviser Jared Kushner and Secretary of State Rex Tillerson.

The president and the pontiff discussed terrorism and the radicalization of young people. The Vatican's secretary of state raised the issue of climate change in the meeting and encouraged Trump to remain in the Paris agreement.

Pope Francis and Trump exchanged gifts during the meeting. Trump gave the pontiff a first-edition set of books written by civil rights leader Martin Luther King Jr., a piece of granite from King's memorial in Washington and a bronze sculpture that "represents hope for a peaceful tomorrow," according to the White House.

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The pope's gifts to Trump also represented peace: the pontiff offered Trump a medal that depicts an olive branch, among other gifts.

"We can use peace," the president said upon receiving the gift.

The pope presented Trump with the medal, a message of peace and three bound papal documents that to some degree define his papacy and priorities, including the family and the environment. The pope told Trump he signed the message "personally for you." Trump said he would read the books.

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When Trump departed, he told the pope: "Thank you, I won't forget what you said."

Later, as he met with Italian Prime Minister Paolo Gentiloni, Trump said of the pope: "He is something."

"We had a fantastic meeting," the president said. "It was an honor to be with the pope."

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

The Associated Press contributed to this report.