By Susan Cornwell and Ian Simpson
WASHINGTON (Reuters) - In his first public words on his first trip to the United States, Pope Francis on Wednesday put himself in the shoes of millions of foreigners.
"As the son of an immigrant family, I am happy to be a guest in this country, which was largely built by such families," the Argentine pontiff told U.S. President Barack Obama, speaking slowly in English after months of study.
And with those words, the first pope from Latin America became an advocate for millions from his home region and from other places who have chosen to immigrate to the United States, where 11 million undocumented immigrants have created a political problem far from being solved.
In recent months, immigration has moved up the U.S. political agenda and several Republican presidential candidates like front-runner Donald Trump have advocated deporting all undocumented immigrants, building a wall along the U.S.-Mexico border and ending birthright citizenship.
Later in the day, Francis thanked U.S. bishops for welcoming and integrating immigrants and asked them to continue.
"Now you are facing this stream of Latin immigration which affects many of your dioceses," he said, speaking in Italian. "Not only as the Bishop of Rome, but also as a pastor from the South, I feel the need to thank and encourage you."
John Raphael Quinn, the archbishop emeritus of San Francisco, liked the pope's emphasis on immigrants and believes he will bring it up again Thursday when he addresses a joint session of the U.S. Congress, a first for a pope.
"It's a very important thing, especially when you see 60 million people displaced in the world today," said Quinn. "That's not a political problem; that's a huge human problem. Everywhere, it's a world problem."
To underscore his concern for the plight of migrants, Francis chose to make his first trip after his election in 2013 to the tiny southern Italian island of Lampedusa to pay tribute to the thousands who drowned trying to cross the Mediterranean.
This month, he asked parishes in Europe to house refugee families, many from Syria, as Europe struggles with its migrant crisis.
Daniel Garcia, who was made an auxiliary bishop of Austin, Texas, earlier this year, said the pope's message on immigration was "that we need not fear the challenges that lie ahead, the political rhetoric."
Many Hispanic families turned out to see Pope Francis travel down Washington streets, wearing "Yo (heart) El Papa" buttons and shouting out to "Papa Francisco." And one immigrant family from El Salvador got a thrill when the pope spotted their five-month-old son Loukas and asked security to bring him over for a papal kiss on the head.
"The pope is the messenger of Christ, and for the pope to bless my child, it's a marvelous thing," said the mother, Iris Chavez, 25.
How Loukas stood out in a crowd 15-deep is unclear, but his mother thinks her son knew something was about to happen.
"He just started smiling as if he knew it was coming," she said.