New Delhi, April 18 -- An American delegation recently met with Cuban government officials in the island nation, marking a renewed diplomatic push even as U.S. President Donald Trump has threatened to intervene and Cuba's leader said this week that his country is prepared to fight if that should happen.

A senior State Department official met with the grandson of retired Cuban leader Raul Castro last week during the trip, according to a department official, who was not authorized to comment publicly and spoke Friday on condition of anonymity to discuss the sensitive matter.

The official did not say who from the U.S. met with Raul Guillermo Rodriguez Castro, whose grandfather is believed to play an influential role in the Cuban government...