Honduras’s president threatened to push the U.S. military out of a base it built decades ago in the Central American country should President-elect Donald J. Trump carry out mass deportations of undocumented immigrants from the United States.

The response by President Xiomara Castro of Honduras, in an address broadcast on television and radio on Wednesday, was the first concrete pushback by a leader in the region to Mr. Trump’s plan to send back millions of Latin American citizens living in the United States.

The threat came as Ms. Castro and Mexico’s president, Claudia Sheinbaum, also called a meeting of foreign ministers later this month to address the deportation issue.

“Faced with a hostile attitude of mass expulsion of our brothers, we would have to consider a change in our policies of cooperation with the United States, especially in the military arena,” Ms. Castro said.

“Without paying a cent for decades,” she added, “they maintain military bases in our territory, which in this case would lose all reason to exist in Honduras.”

Honduras’ foreign minister, Enrique Reina, said afterward in a radio interview that Honduras’s leader had the power to suspend without the approval of the country’s Congress a decades-old agreement with the United States that allowed it to build the Soto Cano air base and operate America’s largest military task force in Central America from there.