Pope Francis is at the Palace of the Revolution, Cuba's seat of government, for a state meeting with President Raúl Castro.
The two men are greeting Cuban cardinals and government officials.
Among those attending is first Vice President Miguel Díaz-Canel, the man widely expected to assume the presidency in 2018 when Castro says he intends to step down.
Previously, Francis met with Fidel Castro at the former Cuban leader's home.
The former president and the Pope are presented in a widely distributed picture look at each other in the eyes as they shake hands. Francis is wearing his white vestments, and Castro is clad in a white, button-down shirt and a sporty sweatshirt.
The image was shot by Alex Castro, Fidel's son and official photographer, and was provided to The Associated Press.
The Vatican spokesman says Pope Francis and Fidel Castro exchanged gifts of books during their half-hour meeting at the former Cuban leader's home.
Federico Lombardi says the pontiff presented Castro with a volume written by a Jesuit who taught him at the Catholic school he attended as a child.
Castro gave the Pope a collection of his own conversations about religion with Brazilian cleric Frei Betto.
Lombardi said that the conversation was informal and took place in the presence of Castro's children and grandchildren.
In the middle of his activities in the island, Francis issued a personal invitation for people to join him in Philadelphia next weekend. Whether a million or more people show up, as projected, remains an open question.
A campaign to encourage attendance at the papal Mass and other events features the slogan "I'll be there."
In a videotaped message the pope says, "I will be there because you will be there! See you in Philadelphia!"
Some travel restrictions have been eased, cutting walking distances. But there are still hotel rooms and plenty of rail passes to be had.
The secured site of the pope's two biggest events is the mile-long Benjamin Franklin Parkway. New estimates put its capacity at about 250,000 people.
Other visitors will have to watch on jumbo TV screens near the parkway or in other locations around the city. Church officials say that was always the plan.
In the morning, the Pope celebrated mass in Havana's Revolution Plaza, in the presence of Argentine President Cristina Fernández and island religious leaders.
Francis used the occasion to beg Colombia's government and largest guerrilla army to end South America's longest-running conflict, saying they cannot allow another failure to derail peace efforts.
"May the blood shed by thousands of innocent people during long decades of armed conflict" helps sustain efforts to find a definitive peace, he expressed.
"Please, we do not have the right to allow ourselves yet another failure on this path of peace and reconciliation."
The church's first Latin American Pope recently helped nudge forward the historic reconciliation between the United States and Cuba with a personal appeal to the leaders of both countries.