PANAMA CITY — President Trump’s top diplomat makes his first trip overseas this weekend, heading to Central America to drive home the message that the U.S. expects cooperation in its mass deportation of immigrants.

But newly confirmed Secretary of State Marco Rubio will need to be careful to avoid alienating long-standing U.S. allies who say they are already taking a robust role in curbing illegal immigration and accepting deportees.

Panama, Rubio’s first stop late Saturday, is an especially delicate case.

Trump further complicated the immigration question by declaring he wants to seize the Panama Canal, the 50-mile waterway that connects the Pacific and Atlantic oceans and is a key instrument in international shipping that Panama has controlled for a quarter-century.

“This matter is closed,” Panamanian President José Raúl Mulino said at a news conference this week. “The canal is Panama’s.”

Mulino refused to contemplate any “process of negotiation” on the canal, which the U.S. ceded to Panama in 1999, ending a long-standing sore spot of U.S. colonization in Latin America.

For many Panamanians, the canal represents income, employment and identity. Last year, operation of the canal by an independent Panamanian commission contributed $2.4 billion to state coffers.

The canal “is an existential asset” for Panama, said John Feeley, former U.S. ambassador to Panama.

The waterway was cleaved across the most narrow section of the Panamanian isthmus in the late 1800s and early 1900s, by French and then U.S. engineers. Thousands of mostly Caribbean workers died from disease and accidents. Then-President Carter in 1977 signed a treaty giving control of the canal to take full effect two decades later.

In terms of seeking Panama’s cooperation on immigration, the Trump administration would be “knocking on an open door,” Feeley said, given Mulino’s eagerness to assist on the issue. But the canal is a different matter.

“On America taking back the canal, that is not going to happen,” he said. “The only way … the United States will take back control of the canal is if there is another military invasion and occupation. And you show me, even among Trump voters, where the appetite for that is. I don’t think you can find it.”

But Trump claims Chinese influence over the canal now poses a threat to U.S. national security. Trump exaggerates that influence, experts say, but it is true that Chinese-controlled firms own part of a port and other assets. China throughout Latin America has made significant inroads in infrastructure and diplomacy, often taking advantage of U.S. inattention.

The canal is “no longer autonomous — they have to do whatever the [Chinese] government tells them,” Rubio said of the Panamanian administration of the canal during an interview with podcast host Megyn Kelly. “And if the government in China, in a conflict, tells them to shut down the Panama Canal, they will have to.”

He added: “So it’s a technicality, but in reality if China wanted to obstruct traffic in the Panama Canal, they could. … And I think the president’s been pretty clear he wants to administer the canal again.”

Rubio has to balance his boss’ demands with attempting to maintain good relations with countries that for the most part are loyal allies to the U.S., starting with Panama.

“Panama has been very helpful in dealing with its border,” Trump’s special envoy for Latin America, Mauricio Claver-Carone, said Friday in previewing Rubio’s trip.

Relations with Colombia have been more strained.

President Gustavo Petro for more than two years received hundreds of deportation flights from the U.S.

But Sunday he turned back two military flights in which migrants had been shackled. He said would continue to accept flights, but wanted “dignified conditions” for Colombian nationals.

Trump immediately threatened a 25% tariff on Colombian exports — mostly roses, coffee and oil — and prevented thousands of Colombians from obtaining visas to the United States.

The two leaders quickly overcame the row and flights resumed. The Trump administration defended its aggressive approach.

“It sends a message that … there will be consequences,” Claver-Carone said.

Rubio will also travel to El Salvador and Guatemala. In El Salvador, Trump administration officials have praised President Nayib Bukele’s mass incarceration of suspected gang members. It is a system Bukele enacted by suspending his country’s constitution, prompting criticism from human rights groups. Trump administration officials cited it as a potential model for dealing with criminal migrants in the United States.

For the first time in modern history, the State Department is top-heavy with Latin America experts, starting with Rubio.

But Trump has singled a more transactional approach. A policy that for decades focused on the fortifying of democratic institutions and human rights will be replaced with rewards for cooperation on immigration, experts say.

The traditional approach of demanding democracy in some ways gave an opening to China, which never made such demands. The U.S., in contrast to China, came with “a bunch of lessons and no goodie bags,” Ryan Berg, who heads the Americas program at the Center for Strategic and International Studies, a think tank in Washington, said in an interview.

Writing in Foreign Policy, Berg said: “Taking the region for granted as a sphere of U.S. influence has come at a high cost, creating a strategic vacuum in which China and lesser great power rivals have advanced their geopolitical aims with minimal pushback.”

Panama’s role in the immigration puzzle has been primarily to repatriate citizens from other countries who end up stranded in the country as they attempt to move northward. These include people from China, Sudan and other far-flung locations.

The Trump administration’s recent temporary freeze of some foreign aid also hurt Latin America, advocates say, crippling lifesaving food and heath programs.