Obama, Raul Castro speak ahead of pope's visit to US, Cuba
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.
Earlier Friday, the U.S. eased rules for citizens wishing to travel to Cuba or do business with its growing ranks of independent entrepreneurs, a step aimed at kindling greater economic freedom on the island.
The U.S. also has concerns about Cuba's human rights record and detainment of political prisoners.