GUATEMALA CITY • As some 3,000 Hondurans made their way through Guatemala, attention turned to Mexico, after President Donald Trump threatened Thursday to close the U.S.-Mexico border if authorities there fail to stop them — a nearly unthinkable move that would disrupt hundreds of thousands of legal freight, vehicle and pedestrian crossings each day.

With less than three weeks before the Nov. 6 midterm elections, Trump seized on the migrant caravan to make border security a political issue and energize his Republican base.

“I must, in the strongest of terms, ask Mexico to stop this onslaught — and if unable to do so I will call up the U.S. Military and CLOSE OUR SOUTHERN BORDER!” Trump tweeted, adding that he blamed Democrats for what he called “weak laws!”

The threat followed another one earlier this week to cut off aid to Central American countries if the migrants weren’t stopped. Trump made a similar vow over another large migrant caravan in April, but didn’t follow through and it largely petered out in Mexico.

On Thursday, Mexico dispatched additional police to its southern border after the Casa del Migrante shelter on the Guatemalan side of the border reported that hundreds of Hondurans had already arrived there.

Mexican officials said the Hondurans would not be allowed to enter as a group and would either have to show a passport and visa — something few have — or apply individually for refugee status, a process that can mean waiting for up to 90 days for approval. They also said migrants caught without papers would be deported.

Marcelo Ebrard, who is set to become foreign relations secretary when President-elect Andres Manuel Lopez Obrador takes office Dec. 1, said Trump’s tweets need to be understood in the context of the upcoming U.S. midterm elections.

“The electoral process is very near, so he is making a political calculation,” Ebrard said in an interview with Radio Centro.

Trump’s stance, he said, was “what he has always presented,” adding he saw “nothing surprising in it.”

Still, the idea that Mexico could close its porous southern border — or that the United States would choke off the lucrative trade and other traffic between the two nations — strained the imagination.

“There would be huge economic impacts for both the United States and Mexico … but limited effect on illegal immigration,” said Andrew Selee, president of the Migration Policy Institute.

“The president certainly can slow down crossing at legal border crossings where about a million people cross each day. That would really hurt legal transit between the two countries and manufacturing and trade, which would affect American workers,” Selee said. “But it would have much less impact on illegal border crossings between ports of entry.”

Stephanie Leutert, director of the Mexico Security Initiative at the University of Texas at Austin, said she interpreted the tweet to mean Trump could send troops not to ports of entry but elsewhere where the illegal crossings take place.

“If that’s the case, I don’t think Mexico should be too worried because in a sense … it’s the same kind of thing U.S. administrations have been doing for a long time,” Leutert said.

Honduran migrants bound to the U.S border climb into the bed of a truck in Zacapa, Guatemala, on Wednesday. The group of about 2,000 Honduran migrants hit the road in Guatemala again Thursday, hoping to reach the United States despite President Donald Trump’s threat to cut off aid to Central American countries that don’t stop them.

the associated press