In an interview with "Face the Nation," Gates said another mass exodus from Cuba is the "biggest risk."

"This has become a very strong interest to the White House, and it doesn't appear to be going away or wavering," one expert said.

The visit comes as the island deals with a collapse of its energy sector amid rising tensions with the US.

Cuba’s top diplomat in the U.S. said the country is sticking to its red lines amid faltering negotiations it says have made “no progress” and a looming threat from President Trump to invade the nation.

NBC's Tom Llamas presses Secretary Rubio about $100-million aid package being offered to Cuba by the U.S. amid the island's worst electricity blackouts in decades and escalating poverty. MARCO RUBIO,

CIA Director John Ratcliffe makes a surprise visit to Cuba as the spy agency calls on the nation to make "fundamental changes." Cuba says it has run out of fuel and is suffering massive blackouts.

President Trump has continued to dangle the possibility of military action against Cuba, appearing to be emboldened by his administration's intervention in Venezuela. He suggested earlier this month that "on the way back from Iran,

With Cuba out of diesel and food rations shrinking, the communist government is leaning on once-shunned private businesses to keep the island’s paralyzed economy from total collapse. A revived Trump administration has tightened an energy blockade,