Pope Francis urged Central American governments on Sunday to find an urgent solution to help thousands of U.S.-bound Cuban migrants stranded on the border between Costa Rica and Nicaragua.

Nicaragua has refused to let the growing number of Cubans trying to reach the United States who have become stuck in Costa Rica pass through its territory. About 5,000 Cubans are estimated to be on the border.

Speaking from his window overlooking St. Peter's Square to ten of thousands of people gathered for his Sunday blessing, Francis said many of those stranded were victims of human trafficking.

"I ask the countries of the region to generously resume efforts to find a quick solution to this humanitarian drama," he said.

Central America and Mexico have seen a surge in migrants from the Communist-ruled island as the process of a detente between Washington and Havana raises the prospect that current U.S. asylum rights for Cubans may soon end.

Last week the Nicaraguan government proposed that the U.S. government organize an airlift to take the migrants directly from Costa Rica to the United States. The Costa Rican government has tried to convince both Belize and Guatemala to allow the Cubans passage to reach Mexico.

The plight of migrants is expected to be a main topic of Francis' trip in February to Mexico, where he will say Mass at Ciudad Juarez within sight of the border with Texas..

Earlier on Sunday, Francis said Mass in St. Peter's Basilica for families in Rome marking the Roman Catholic Church's jubilee year.