Pope Francis has arrived in the United States for his first visit - a historic six-day trip during which his focus on consumerism, poverty and the marginalised risks being seen as a criticism of American society.
The 78-year-old Argentine pontiff stepped onto US soil for the first time at Andrews Air Force Base outside Washington, where he was greeted by US President Barack Obama, his wife Michelle and their two daughters, after making a tour of communist-ruled Cuba.
US Catholic leaders and a select crowd of several hundred well-wishers were on hand to greet the Pope, who wore his traditional papal whites and waved to the crowd, who chanted: "Ho ho, hey hey, welcome to the USA".
Obama will host the Jesuit Pope at the White House on Wednesday.
"When the president sits down with Pope Francis tomorrow in the Oval Office, the president will not arrive at that meeting with a political agenda," White House spokesman Josh Earnest told reporters.
"This is an opportunity for two men who have so many values in common to talk about the efforts that they are making in their respective and quite different roles to advance those shared values."
Asked at a briefing why Obama has gone to "these lengths" to greet the Pope, Earnest said: "Pope Francis, we have seen, has really struck a chord in people not just across the United States but around the world. He serves as a source of inspiration not just for Catholics but of people of frankly all religions around the world."
Francis will make two key speeches during his visit, addressing Congress on Thursday and the United Nations on Friday.
The topics in his addresses will include critiques of the dominance of finance and technology, a condemnation of world powers over the conflicts gripping the planet, appeals to protect and welcome immigrants, and climate change, according to Vatican sources.
On Tuesday, he travelled in a Fiat 500 to the Vatican's diplomatic mission in Washington, where he will be staying, eschewing larger, more polluting vehicles.
The visit will take place under tight security, with US authorities dealing with the complexities of protecting a Pope who insists on travelling in an open vehicle to be closer to the masses.
Authorities are facing a particular security headache in New York, where Francis plans to criss-cross Manhattan at a time when 170 world leaders will be in town for the UN General Assembly
He will preside over an inter-faith ceremony at Ground Zero, visit a Harlem Catholic school and greet crowds on a procession through Central Park.
He will wrap up his trip Saturday and Sunday in Philadelphia at an international festival of Catholic families.
In the United States the Pope will find an American public that widely respects him, but has a less favourable view of the Catholic Church.
While 81 percent of Catholics have a positive view of the Church, only 55 percent of America's roughly 70 million Catholics as a whole do, according to a recent poll.
And for some critics, the dominant themes of his papacy - his critique of consumerism, calls to embrace poverty and condemnation of a "throwaway culture" - sound remarkably like an indictment of the American way of life.
The pope has been active in urging compassion, including for those historically shunned by the Church, and for calling for action against economic inequality and environmental degradation.
Americans in general approve of those efforts, with 54 percent wanting him to "continue as he has been" and another 23 percent urging him to be even more active.