Since assuming the Mexican presidency 14 months ago, Andres Manuel Lopez Obrador has thrown huge resources behind Trump's goal of cutting illegal migration from Central America, discarding his own view in 2017 that likened the American's treatment of migrants to Nazi Germany's persecution of Jews.

Threatened with tariffs by Trump, Lopez Obrador has sent thousands of National Guard troops to police Mexico's borders. The result, reportedly, is a more than a 70 percent drop in migrant detentions on the U.S.-Mexico frontier since last May. Obrador's National Guard is now widely viewed as a de facto wall against migrants reaching the U.S. border.

"(It's) submission and political obedience, not free self-determination," said Enrique Vidal of human rights group Fray Matias de Cordova, who watched the National Guard rounding up a caravan of Central American migrants on Mexico's southern border last week to avert a fresh conflict with Trump.

Since Lopez Obrador agreed in June to tighten the border, tensions have eased. But Trump still says Mexico must pay for his planned border wall and he has used ongoing gang violence to press for more cooperation on migration and security. Trump claimed this week that his border wall was "ultimately and very nicely being paid for by Mexico."

Lopez Obrador sidestepped the question when asked to respond to Trump at a news briefing on Wednesday, casting criticism of his migration policy as an attempt by adversaries to draw him into a dispute with the United States.

"He's like a matador facing Trump who's like a bull that charges you at will," said Lorenzo Meyer, a historian at the Colegio de Mexico and friend of Lopez Obrador. He claimed that it is against the nature of Obrador to be so "polite," but "he doesn't have another (option)."