ROME — As US President Barack Obama and Cuban President Raul Castro exchanged a handshake on Friday more than five decades in the making, one that Pope Francis played a lead role in making possible, the pontiff urged leaders of the Americas to go beyond such gestures by attacking poverty at its roots.

“I am convinced that inequality, the unfair distribution of wealth and resources, is a source of conflict and violence among peoples,” the pope said, “because it assumes that the progress of some is built on the necessary sacrifice of others and that, to live in dignity, we must fight against others.”

The comments came in a letter from Pope Francis to the seventh annual Summit of the Americas, taking place in Panama City. This year’s summit is of special interest because of the changed climate between the United States and Cuba following the resumption of relations last December.

Obama and Castro met one another and shook hands during an opening dinner Friday night. They were expected to have more substantive exchanges both Saturday and Sunday.

In a personal message to the heads of state, Francis seemed to suggest that merely being polite to one another is not enough. To end conflict, he insisted, governments must address its underlying causes.

It’s unacceptable, the pope said, “to expect the poor to gather the crumbs that fall from the table of the rich.”

History’s first Latin American pope said he felt “in sync” with the theme chosen for the summit, which is “Prosperity with Equity: the Challenge of Cooperation in the Americas.”

Francis said that well-being achieved through inequality is unfair at its roots, and undermines the dignity of all. There are basic “commodities,” the pope said, such as land, work, and home, and “public services” such as health, education, safety, and protection of the environment, “from which no human being should be excluded.”

In what has become a signature phrase, the pontiff called for a “globalization of solidarity and fraternity,” instead of the globalization of discrimination and indifference.

Francis cautioned the leaders that even though it’s “undeniable” many countries have experienced strong economic growth in recent years, others are still mired in poverty. Moreover, he said, in emerging economies, there’s a widening gap between the rich and the poor.

Direct actions to favor the disadvantaged, as with the smallest members of a family, “should be a priority for policymakers,” Francis said in the letter, which was read to the summit by Italian Cardinal Pietro Parolin, the Vatican’s secretary of state.

The pope also spoke about immigration, one of many topics he’s expected to raise when he addresses a joint session of the US Congress next September. He said that the vast economic disparity between countries forces many people to leave their land and family, “becoming easy prey for traffickers and slave labor.”

Francis argued that a lack of cooperation among countries leaves many people outside of the legal system and unprotected, forcing them to resign themselves to becoming victims of abuse.

“Sometimes even within countries, outrageous and offensive differences, especially in indigenous populations in rural areas or suburbs of large cities, occur,” Francis said. “Without an authentic defense of these people against racism, xenophobia, and intolerance, the state of law would lose its legitimacy.”

The Summit of Americas brings together leaders of 35 countries from North, Central, and South America. This year marks the first time Cuba is participating, a direct result of the reopened dialogue with the United States.

When announcing the historic restoration of the relations in early December 2014, both Obama and Castro thanked Pope Francis for his “key role” in the process.