Pope Francis appealed to the United States Wednesday to take urgent action and help slow the pace of climate change, because the world is at "a critical moment of history."
President Barack Obama warmly welcomed the leader of the Roman Catholic Church to the White House on a beautiful autumn morning in Washington, and he agreed that Americans and people throughout the world have "a sacred obligation to protect our planet."
The president and the pope were speaking at an official arrival ceremony celebrating the pontiff's first visit to the United States. They saluted each other in speeches that were frequently interrupted by applause from 15,000 invited guests on the White House lawn.
Crowds of other well-wishers turned out to get a glimpse of the pope from afar.
"What a beautiful day the Lord has made," Obama said, adding that the pope's "message of love and hope has inspired so many people, across our nation and around the world."
Turning to the 78-year-old pope, the president praised the pontiff for "your humility, your embrace of simplicity, the gentleness of your words and the generosity of your spirit."
"You remind us that in the eyes of God our measure as individuals, and as societies, is not determined by wealth or power or station or celebrity, but by how well we hew to Scripture’s call to lift up the poor and the marginalized, to stand up for justice and against inequality," Obama said.
The president's speech referenced refugees fleeing war-torn lands, religious liberty and the "sacred obligation to protect our planet." He also thanked the pope for his efforts to bring Cuba and the United States closer together after decades of distrust.
Pope Francis highlighted his background -- born in Argentina to parents who emigrated from Italy to South America -- in his opening speech.
"As the son of an immigrant family, I am happy to be a guest in this country, which was largely built by such families," he said. "I would like all men and women of good will in this great nation to support the efforts of the international community to protect the vulnerable in our world."
Francis called on Americans to take urgent steps to prevent environmental ruin and also to address poverty. "When it comes to the care of our 'common home,' we are living at a critical moment of history," he said in echoing his June encyclical on the environment.
Addressing climate change "can no longer be left to a future generation," he added.
And for all the United States has done and continues to do in addressing world problems, the pope said in conclusion: "God bless America."
The two leaders then went inside the White House for private talks in the president's Oval Office. Together with first lady Michelle Obama, they also waved to the crowd from a balcony of the presidential mansion.
During the rest of his first full day in the United States, Francis will speak to U.S. Catholic bishops and celebrate Mass at the national shrine of the U.S. Catholic church, the Basilica of the Immaculate Conception. During the service the pope is to canonize -- raise to sainthood -- an 18th-century Spanish missionary who spread the word of the church in what is now California.
White House officials said the pope and the president have many shared values, on social justice, climate change and other issues.
Some conservatives have criticized Francis' economic views, calling them Marxist, but the pope has defended himself against what he contends is an inaccurate description of him as "left-leaning."
While flying to the United States from Cuba Tuesday, Francis told reporters: "I am certain that I have never said anything beyond what is in the social doctrine of the church. It is I who follow the church. ... My doctrine on all this ... on economic imperialism, is that of the social doctrine of the church."
Pope Francis has also spoken out against the persecution of religious minorities – particularly in the Middle East, where Islamic State militants have targeted Christians and Yazidis in deadly attacks. This commitment to religious liberty and the rights of religious minorities is another value he shares with Obama, the president's advisers say.
In contrast, Obama and the pope differ sharply on issues, such as abortion and same-sex marriage.
Tens of thousands of people eager to see the pope were expected to pack the streets of the national capital Wednesday -- around the Washington Monument and National Mall, around the national shrine in the northern part of the city and near the home of the Vatican's papal nuncio (ambassador) to the United States, where Francis is staying while in Washington.
Before departing for the White House Wednesday morning, Pope Francis stopped to talk to people gathered outside the Apostolic Nunciature, the Vatican's Embassy, where he is staying while in Washington.
After his meeting with Obama Wednesday, Francis took part in a parade around the National Mall.
Later, he will hold a prayer meeting with U.S. bishops and celebrate a Mass canonizing Junipero Serra, the Franciscan friar who founded Catholic missions along the coast of California while marching with Spanish conquistadors.
Serra's elevation to sainthood is a sore point for many Native Americans, who say Serra contributed to the abuse and elimination of many indigenous tribes from enslavement and disease.
Earlier at the South Lawn welcoming ceremony, Christina Toth from Boyds, Maryland, said, "I feel like this is a pope for the people. He stands for all of humanity and power and he seems very approachable. We haven't seen that in a pope before."
Toth said she is a Catholic, "more so now than any other time in my life," due to Francis' papacy.
Ben Paracchio of Asheville, North Carolina, said, "This is a historic moment. I'm really fortunate that I get to be here. I really admire this pope and all that he stands for."
Margarita Fuentes of Washington, D.C., bur originally from El Salvador, stood for six hours to get a chance to see and hear the pope on the South Lawn during the arrival ceremony, but says "It was worth it, it was amazing."
"I am 200 percent Catholic and agree with everything he does. He is going to save our lives, nations, and communities all over the world,” Fuentes said. "He really feels the pain of every single human being. We are blessed to have a pope like him."
The pope arrived in the United States Tuesday after a historic visit to Cuba and the Vatican hosted U.S. and Cuban delegations last December as both sides finalized an agreement.
Obama last met with the pontiff at the Vatican in March of 2014 – but it is the first time the pontiff has set foot on American soil.
On Thursday, Francis becomes the first-ever pope to deliver an address before a joint meeting of Congress.
He will travel to New York City Friday to address the United Nations General Assembly.
On Saturday morning, he'll travel to Philadelphia for this weekend’s Vatican-sponsored World Meeting of Families.
On Sunday, he will celebrate an outdoor Mass, which is expected to draw about 2 million people.
During their one-on-one meeting at the White House, Obama presented Francis with two gifts: a sculpture of an ascending dove, an international symbol of peace as well as the Christian symbol for the Holy Spirit; and a key from the Maryland home of Elizabeth Ann Seton, the first native-born American to be declared a saint.
Richard Green contributed to this report. Some material for this report came from Reuters and AP.