Pope Francis headed for Washington on Tuesday for the first visit of his life to the United States, bringing his "church of the poor" to the world's wealthiest superpower and a country polarized over issues closest to his heart: immigration, social injustice and economic inequality.

President Barack Obama planned to greet Francis on the tarmac at Andrews Air Force Base upon his arrival from Cuba, according a rare honor to the pontiff.

During his six-day, three-city visit to the U.S., the pope will meet with Obama, address Congress, speak at the United Nations in New York and take part in a Vatican conference on families in Philadelphia.

He is expected to urge America to take better care of the environment and the poor and return to its founding ideals of religious liberty and open arms toward immigrants.

Francis' enormous popularity, propensity for wading into crowds and insistence on using an open-sided Jeep rather than a bulletproof popemobile have complicated things for U.S. law enforcement, which has mounted one of the biggest security operations in American history to keep him safe.

The measures are unprecedented for a papal trip and could make it nearly impossible for many ordinary Americans to get anywhere close to Francis. For anyone hoping to get across town when the pope is around, good luck.

For all the attention likely to be paid to Francis' speeches, including the first address from a pope to Congress, his more personal gestures — visiting with immigrants, prisoners and the homeless — could yield some of the most memorable images of the trip.

"What the pope does in the United States will be more important than what he says," said Mat Schmalz, a religious studies professor at Holy Cross College in Worcester, Massachusetts. "There are a lot of things he will say about capitalism and about wealth inequality, but many Americans and politicians have already made up their minds on these issues. What I would look for is a particular gesture, an unscripted act, that will move people."

In Cuba, Francis basked in the adulation of Cubans grateful to him for brokering the re-establishment of diplomatic relations between the U.S. and the communist island. The pope is expected to raise the "normalization" process while in Washington, where Congress alone can lift the embargo long opposed by the Vatican.

He arrives at a moment of bitter infighting across the country over gay rights, immigration, abortion and race relations — issues that are always simmering in the U.S. but have boiled over in the heat of a presidential campaign.

Capitol Hill is consumed by disputes over abortion and federal funding for Planned Parenthood after hidden-camera videos showed its officials talking about the organization's practice of sending tissue from aborted fetuses to medical researchers. While Francis has staunchly upheld church teaching against abortion, he has recently allowed ordinary priests, and not just bishops, to absolve women of the sin.

Francis' visit comes three months after the U.S. Supreme Court legalized gay marriage, putting U.S. bishops on the defensive and sharply dividing Americans over how much they should accommodate religious objectors. The pope has strongly upheld church teaching against same-sex marriage but adopted a welcoming tone toward gays themselves, saying, "Who am I to judge?" when asked about a supposedly gay priest.

Americans are also wrestling anew with issues of racism. A series of deaths in recent years of unarmed black men at the hands of law enforcement has intensified debate over the American criminal justice system. Francis will see that system up close when he meets with inmates at a Pennsylvania prison.

U.S. bishops, meanwhile, expect Francis will issue a strong call for immigration reform, a subject that has heated up with hardline rhetoric from some of the Republican presidential candidates, especially Donald Trump. He has painted Mexican immigrants as criminals and said he would build a wall along the U.S. southern border and force Mexico to pay for it.

Francis will be sending a powerful message on that front by delivering the vast majority of his speeches in his native Spanish.

"Our presidential candidates have been using immigrants as a wedge issue," Miami Archbishop Thomas Wenski said. "It's our hope that the visit of Pope Francis will change this narrative."

The issue is particularly dear to Francis: He took his first trip outside Rome to the island of Lampedusa, ground zero in Europe's immigration crisis, and recently urged every parish and religious order to take in a refugee family. The Vatican itself is sheltering a Syrian family.

Francis' most eagerly watched speech will be his address Thursday to Congress. Republicans and many conservative Catholics have bristled at his indictment of the excesses of capitalism that he says impoverish people and risk turning the Earth into an "immense pile of filth."

Some conservative Catholic commentators have urged Francis to spend more time fighting abortion and gay marriage instead of focusing on the environment. Catholic GOP presidential candidates have rejected his arguments as flawed, and one Republican climate doubter, Arizona Rep. Paul Gosar, announced plans to boycott Francis' speech.

Nevertheless, Francis enjoys popularity ratings in the U.S. that would be the envy of any world leader. A New York Times/CBS News poll conducted last week found 63 percent of Catholics have a favorable view of Francis, and nearly 8 in 10 approve the direction he is taking the church.

Just how far Francis presses his agenda in Washington is the big question.

Paul Vallely, author of "Pope Francis, The Struggle for the Soul of Catholicism," said to expect both "warmth" and "some finger-wagging" from the pope.

"He won't necessarily confront people head-on," Vallely said, "but he'll change the priorities."