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The Trump administration says it will impose those tariffs if Mexico doesn't stop the flow of migrants at the U.S. border; immigration experts question whether that's something Mexico can do. As NPR's Joel Rose reports, Mexico's enforcement is already stretched thin by the flow of migrants from Central America.
JOEL ROSE, BYLINE: The White House says Mexican authorities could easily halt the flow of migrants crossing their country en route to the U.S., and the head of the Border Patrol Union agrees.
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BRANDON JUDD: Yeah, because we've seen it before. I mean, we already have a history of this. And it has worked, so this presumably would obviously work again.
ROSE: That's Brandon Judd, speaking today on NPR's Morning Edition. Mexican authorities helped limit the surge in unaccompanied children coming to the U.S. in 2014, for example, by discouraging them from travelling on La Bestia, the freight trains that migrants use to travel the length of Mexico. Former border security officials say cooperation from the Mexican government has been important in the past, but those same experts are skeptical that the Trump administration's ultimatum will suddenly stop the huge numbers of migrants crossing the southern border each month.
JOHN SANDWEG: This is a massive problem. And Mexico doesn't have the border security infrastructure that we have in the U.S.
ROSE: John Sandweg is a former head of U.S. Immigration and Customs Enforcement under President Obama. He says Mexico's immigration forces are much smaller than their U.S. counterparts. They, too, have been overwhelmed by the huge number of migrants from Guatemala, Honduras and El Salvador. Most are families and children fleeing from violence and poverty. Gustavo Mohar served as Mexico's undersecretary for migration during the Bush and Obama administrations. He says Trump's demand is unreasonable.
GUSTAVO MOHAR: Asking Mexico to deter desperate people that will do anything they can to try to at least have a chance to save their lives is asking for something impossible to achieve.
ROSE: The White House says Mexico could, quote, "quickly and easily," unquote, stop migrants from crossing its southern border with Guatemala. NPR has reported that Central American migrants move easily across that border on foot through the jungle or at official checkpoints where smugglers have paid off immigration officials. For Mexico to really grapple with this problem, experts say it would have to beef up its immigration forces and root out corruption. But that will take time and an outsized effort.
ANDREW SELEE: President Trump keeps going for the quick fix. But there isn't a quick fix, and there isn't a quick fix in what the U.S. government can do, and there isn't a quick fix in what the Mexican government can do.
ROSE: Andrew Selee is president of the nonprofit Migration Policy Institute in Washington.
SELEE: Essentially, what you see is the U.S. government hasn't been capable of figuring out how to respond to this massive flow. And Trump seems to be throwing the ball to the Mexican government to do it, but they also are not in a position to do much more.
ROSE: Selee says the Mexican government already does cooperate with U.S. immigration authorities. It's deported tens of thousands of Central American migrants and allowed thousands more to stay in Mexican border towns while they wait for their day in U.S. immigration courts under the Trump administration's controversial Remain in Mexico policy. John Sandweg says right now the Mexican government takes back its deported nationals quickly.
SANDWEG: The administration just needs to be very careful here because if Mexico dials back their cooperation, things can get a lot worse very quickly.
ROSE: Making a bad situation at the border even worse.
Joel Rose, NPR News, Washington. Transcript provided by NPR, Copyright NPR.