In attempts to establish closer ties with Cuba, President Obama and President Raúl Castro of Cuba met Saturday, in the first face-to-face discussion between the leaders of the two countries in a half century.

The meeting on the sidelines of the Summit of the Americas was an important step for Mr. Obama as he seeks to ease tensions with Cuba and defuse a generations-old dispute that has also affected relations with the countries of the region.

Ever since his first foray to the summit three months after taking office, Mr. Obama has seen one bone of contention frustrate his efforts to reach out to America’s hemispheric neighbors: the fact that Cuba was blackballed from the gathering, the New York Times reports.

He was scolded by Argentina’s president for maintaining an “anachronistic blockade,” lectured by Bolivia’s president about behaving “like a dictatorship,” and, in 2012, blamed for the failure of leaders to agree that year on a joint declaration — the result, his Colombian host said, of the dispute over Cuba.

This year, Mr. Obama came to the summit meeting here determined to change the dynamic with a series of overtures to Cuba.