Pope Francis wrapped up his trip to Cuba Tuesday with a parting call for reconciliation, before leaving the Caribbean island for what could be a slightly chillier reception in the United States.

The pope, who played a key role in brokering the old Cold War foes' recent rapprochement, delivered mass Tuesday in the Cuban city of Santiago, cradle of the communist island's 1959 revolution, calling for a new kind of "revolution."

Speaking at a basilica to Our Lady of Charity of El Cobre, Cuba's patron saint -- a mixed-race Mary that symbolizes the island's intertwined Spanish and African roots -- he praised Mary as the embodiment of a "revolution of tenderness."

He urged Cubans to follow her example "to build bridges, to break down walls, to sow seeds of reconciliation," in comments that appeared to allude to the nascent reconciliation across the Florida Straits.

Francis then addressed an audience of families, asking for their prayers as he prepares for a synod on the family next month that has unleashed internal conflicts among the Roman Catholic clergy over sensitive issues such as divorce, homosexuality and unmarried couples.

After blessing the southeastern city, Cuba's second-largest, Francis will fly out for his first-ever visit to the United States.

President Barack Obama and First Lady Michelle are to greet him at Andrews Air Force Base outside Washington at the start of an itinerary that includes landmark speeches to Congress and the UN General Assembly.

Francis, 78, has received a warm welcome in Cuba, where he is immensely popular for his role in fostering the thaw that saw Washington and Havana restore diplomatic ties in July after more than half a century.

He has had a packed schedule since arriving Saturday afternoon -- three cities, three masses, various blessings and prayer services, countless handshakes with adoring crowds, and meetings with both Fidel and Raul Castro, the brothers who have ruled the Caribbean island since its 1959 revolution.

He has at times looked tired in the tropical heat, but that has done little to dampen the enthusiasm of the fans and faithful who have flocked to see the first Latin American pontiff.

The Argentine pope is broadly popular in the United States, as well -- 70 percent of Americans approve of him, according to one recent poll, compared to 80 percent of Cubans, in a separate poll.

But for some observers, the dominant themes of Francis's papacy -- concern for the poor, his strong stance in favor of action on global warming and his critique of consumerism -- can be read as an indictment of the American way of life.

That was underlined ahead of his trip when Republican Congressman Paul Gosar, who is Catholic, declared he would boycott the pontiff's historic address to Congress to protest his "leftist" views.

The pope will not have won over such conservative critics with his Cuba visit, during which he has discreetly refrained from chastising the communist regime for its crack-downs on dissidents and curbs on civil liberties.

- Tight security -

Francis is expected to be more provocative in the United States when he addresses Congress Thursday and the United Nations Friday.

The Jesuit pope carefully prepared his speeches for Washington and New York all summer long.

His topics 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, including a bold appeal for a radical revolution of the energy industry and a slowdown in growth.

His visit will take place under tight security, with US authorities nervous over the complexities of protecting a pope who insists on traveling in an open vehicle to be close to the masses.

The visit poses 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 in the south, visit a Harlem Catholic school in the north and greet the crowds on a procession through Central Park.

He will deliver the final mass of his trip Sunday in Philadelphia at an international festival of Catholic families.