Pope Francis met with Fidel Castro Sunday at the Cuban revolutionary leader's home in Havana after an outdoor mass attended by hundreds of thousands of people on the city's iconic Revolution Square.

In what is sure to become an emblematic moment of Francis' tour of Cuba and the United States -- the Cold War enemies whose reconciliation he helped to bring about -- the pope chatted with the 89-year-old Castro and his family for about 30 or 40 minutes, said Vatican spokesman Federico Lombardi.

President Barack Obama and Cuban President Raul Castro had a rare phone call Friday ahead of Pope Francis' impending visit to both their nations.

The White House said Obama and Castro commended the pope's role in "advancing relations between our countries." Francis was instrumental in the secret talks that led to a thaw in relations between the Cold War foes, even offering the Vatican as a neutral location for negotiations.

Pope Francis is likely to meet Fidel Castro during his upcoming trip to Cuba, the Vatican said Tuesday.

"A meeting with Fidel Castro is probable, even if it is not yet scheduled for a specific time in the program," spokesman Federico Lombardi told reporters ahead of the pontiff's eight-day trip to Cuba and the United States, which begins Saturday.

U.S. and Cuban officials met Friday in Havana to set an agenda for future negotiations after having re-established diplomatic relations in July.

The Cuban foreign ministry, which announced the start of the talks on its Twitter account, said the delegations should "define the program of subjects to be taken up immediately" in future sessions.

Cuba's government announced pardons Friday for more than 3,500 prisoners, setting the stage for an eagerly awaited visit by Pope Francis with the largest release of its kind since the 1959 revolution.

The official Communist Party daily Granma published the decision by the Council of State to free 3,522 prisoners "on the occasion of the visit of His Holiness Pope Francis."

Tropical storm Erika broke up as it raked across Cuba on Saturday, drenching the drought-parched island in heavy rain after killing at least 20 people on the Caribbean island of Dominica.

The Miami-based National Hurricane Center later called off all coastal watches and warnings and said the storm had "dissipated" -- a relief for a dozen Caribbean island nations stalked in recent days by Erika.

U.S. Secretary of State John Kerry called Friday for "genuine democracy" in Cuba as the American flag was raised over a U.S. embassy in Havana for the first time in 54 years.

Putting a symbolic capstone on the United States' historic rapprochement with Cuba, Kerry gave the cue to hoist the Stars and Stripes over the glass-and-concrete building on the Havana waterfront.

Fidel Castro marked his 89th birthday Thursday by insisting the United States owes Cuba "many millions of dollars" because of the half-century-old American trade embargo.

Castro spoke out in an essay published in local media a day before U.S. Secretary of State John Kerry makes a historic visit to Cuba to reopen the U.S. embassy as part of the countries' restoration of diplomatic relations.

The United States is "deeply concerned" about arrests of dissidents in Cuba but this will not affect a landmark visit to Havana by U.S. Secretary of State John Kerry, the State Department said Monday.

About 90 activists, some wearing masks in the image of U.S. President Barack Obama, were briefly detained Sunday during a march in Havana led by the Ladies in White, a dissident group founded by wives of political prisoners.

With tense bilateral ties recently renewed after five decades, and top U.S. diplomat John Kerry due in Havana in days, Cuba briefly detained about 90 activists on Sunday.

Cuban security forces rounded up about 50 protesters with the Ladies in White dissident group and around 40 other activists, some wearing masks with the image of U.S. President Barack Obama, according to an Agence France Presse reporter.