Pope Francis began a 10-day trip to Cuba and the United States on Saturday, embarking on his first trip to the onetime Cold War foes after serving as secret mediator of their historic rapprochement. He will be offering a show of solidarity with Cubans and delivering the message in the United States that Hispanics are the bedrock of the church there.

The first Latin American pope will become the first pontiff to address the U.S. Congress and will also proclaim the first saint on U.S. soil by canonizing the missionary, Junipero Serra.

With his arrival in Havana, where he was greeted by President Raul Castro, he became the third pontiff to visit Cuba in the past 17 years — a remarkable record for any country, much less one with a small community of practicing Catholics.

It's largely unknown territory for the 78-year-old Argentine Jesuit, who has never visited either country and confessed that the United States was so foreign to him that he would spend the summer reading up on it. His popularity ratings are high in the U.S., but he also has gained detractors, particularly among conservatives over his critiques of the excesses of capitalism.

Such criticisms have endeared him to Castro, who vowed earlier this year that if Francis kept it up, he would return to the Catholic Church.

But Francis has also been on record criticizing Cuba's socialist — and atheist — revolution as denying individuals their "transcendent dignity."

The visit began in Havana, where he is being greeted as something of a hero to Cubans who rightly credit him with helping restore diplomatic relations between the United States and Cuba. Francis issued a personal appeal to Presidents Barack Obama and Raul Castro last year to end 50 years of animosity, and later hosted the Cuban and U.S. delegations to finalize the deal.

"This visit is like a breath of hope blowing over Cuba, more than anything because of the role that the pope played in the reestablishment of relations," said Diego Carrera, a 71-year-old retired state worker in Havana.

The Cuban government launched a citywide effort to bring crowds into the streets of the capital, offering a day's pay, snacks and transportation to state workers who gathered along the pope's route from the airport to the papal ambassador's home.

The Vatican secretary of state, Cardinal Pietro Parolin, said the Holy See hopes the rapprochement will soon be followed by the removal of the U.S. embargo, which the Vatican has long opposed. On Friday, the United States eased rules for U.S. citizens wishing to travel to Cuba and simplified procedures for telephone and Internet investments and money transfers to Cuba.

But a close Vatican aide of the pope's, Guzman Carriquiry, said Francis' key aim in travelling to Cuba was pastoral, not political.

"When I asked the Holy Father if he's going to Cuba to follow the negotiations between the U.S. and Cuba, he responded clearly this is neither the motivation nor the objective of the trip," Carriquiry told a recent church conference. "The motive of the trip is to confirm the Catholic faith of Cubans and encourage a church that has suffered in the past decades."

That's not to say there won't be politics on the agenda: It will just take place behind closed doors.

Asked if Francis would meet with dissidents or speak out about their plight while in Cuba, the Vatican spokesman, the Rev. Federico Lombardi, said the issue could come up in private discussions between Francis and Raul Castro, and their respective secretaries of state.

"You can discuss problems of this type without dealing with them in clamorous ways," Lombardi said.

Francis will travel to the eastern Cuban city of Santiago to pray at the sanctuary of Cuba's patron saint and stop in the city of Holguin en route, demonstrating once again his desire to visit the most peripheral of places that often get overlooked.

Francis arrives in Washington on Sept. 22 for the U.S. leg of his trip, greeted at Andrews Air Force Base by the first family.

The U.S. visit, planned well before the Cuban stop was added on, will be notable for the center stage Francis is giving Hispanics, who make up about 38 percent of adult Catholics in the U.S., according to the CARA research center at Georgetown University.

Francis will deliver most of his speeches in his native Spanish, even though he speaks very good English. He will meet with immigrants on several occasions and bless a wooden cross particularly important to the Hispanic faithful. His canonization of the Spanish-born Junipero Serra, who built missions across California in the 18th century, is aimed at giving Latino Catholics a role model even though Native Americans have opposed the canonization and argued he helped wipe out indigenous populations.

Most importantly, Francis is expected to make immigration one of the major themes of the visit. Francis has called for countries to be more welcoming of migrants seeking a better life for themselves and decried in particular the plight of would-be migrants crossing the U.S.-Mexico border— signaling he has no qualms about wading into a politically charged issue in the U.S. presidential campaign.

Carriquiry, the No. 2 in the Vatican's Latin America commission and a longtime Francis friend, said he expected the pope would reaffirm what U.S. bishops have been saying for years: Ministry to Hispanics "is not an add-on to the so-called Anglo-centric official, traditional ministry, but that it has to do with those who already make up almost half of the Catholics in the country, whose evangelization is a main priority of the destiny of Catholicism here."

Another hot-button issue Francis will raise is religious liberty, following the legalization of gay marriage across the country and continued opposition by the U.S. church to the birth control coverage requirement in the Obama administration's health care plan. For Francis though, religious liberty also means denouncing the persecution of Christians by Islamic extremists in the Mideast and Africa.

Technically the reason for the trip is for Francis to participate in the church's World Meeting of Families, a big Catholic rally in Philadelphia to reinforce church teaching on marriage.

Traditional family values are expected to be high on the agenda, especially since the Philadelphia event amounts to the opening act of a major and contentious meeting of the world's bishops on family issues — including gays and divorcees — that gets underway a week after Francis returns to Rome.

The archbishop of New York, Cardinal Timothy Dolan, said he expected Francis would do what his predecessors have done on trips to the U.S.: remind America of its greatness, of its long history of welcoming foreigners and of the freedoms, first sketched out in Philadelphia, that formed the foundation of American democracy and society.

"He will remind of us our nobility," Dolan said in a recent interview in the New York City archdiocese. "He will affirm our heritage and in doing that he'll also remind us of the moral imperative to live up to that."