Pope Francis and President Barack Obama are set to hold private talks at the White House on Wednesday before the pontiff parades through streets of Washington on the first full day of his first visit to the United States.
Francis and Obama see eye-to-eye on some issues like climate change and defense of the poor but are at odds over abortion and gay marriage.
Still, the meeting is expected to be friendly, particularly given the pope's role in mediating last year's resumption of diplomatic ties between Washington and Cuba after a chill that lasted more than half a century.
The 78-year-old Argentine pope closes out his day with a Mass at the one of the most important Roman Catholic churches in the United States, the Basilica of the National Shrine of the Immaculate Conception.
There, he will canonize 18th century Spanish missionary Friar Junipero Serra over the objections of critics who say that Serra suppressed Native American cultures in what is now California.
The pope has surprised some U.S. Catholics with his strong words on climate change and criticism of the excesses of capitalism, with less of an emphasis on issues of sexual morality that some of his predecessors and U.S. bishops had focused on.
But Francis, who some right-wing commentators have denounced as a Marxist, says his positions have not strayed from long-held Roman Catholic teachings.
"I am sure that I have not said anything more than what is in the social doctrine of the Church," he told reporters on the plane from Cuba on Tuesday.
Social doctrine
"It is I who follow the Church ... my doctrine on all this ... on economic imperialism, is that of the social doctrine of the Church."
Bestowing on Francis an honor that few foreign dignitaries receive, both President Barack Obama and Vice President Joe Biden personally greeted the pope on the tarmac after the Alitalia papal plane landed at Joint Base Andrews near the capital.
The pope's priorities line up with some of Obama's policy objectives, while leaving Catholic Republican presidential contenders, many of whom dispute the science of climate change, scrambling to explain their disagreements.
The White House says it has no major political goals for Wednesday's meeting.
"I would not expect a robust discussion of a political agenda. But rather, I think it's an opportunity for the two men to talk about the values that they have in common," spokesman Josh Earnest said.
Obama and the pope agree that the 53-year-old embargo against Cuba should be lifted.
On the plane from Cuba, Francis told reporters he hopes the United States will lift the embargo as a result of negotiations between the two countries but does not plan to raise it in his address to Congress this week.
Tens of thousands of people, both Catholic admirers and curious onlookers, are expected to pack the streets around the Washington Monument and National Mall for a papal parade after the White House meeting.
"I am very excited to have him here. I have had the privilege of seeing three popes and I hope to see this one as well," said Mary Fontaine, as she headed into a lunchtime Mass at a Washington church on Tuesday.
On Thursday, Francis becomes the first pope to address Congress and then travels to New York to address the United Nations and visit the Ground Zero memorial to the victims of the Sept. 11, 2001 attacks.
He closes his trip on Sunday in Philadelphia at a worldwide Catholic gathering on family issues. The concluding Mass there is expected to draw some 1.5 million people.