Hundreds of Mexican soldiers were mobilized on Tuesday to the border with the United States as part of an agreement that halted U.S. tariffs on Mexican imports under the condition the Latin American country cracks down on fentanyl trafficking.

As soon as the sun glints over miles of border fence dividing the United States and Mexico, the engines of cargo trucks packed with auto and computer parts roar to life along border bridges and bleary-eyed workers file into factories to assemble a multitude of products geared toward the U.

President Donald Trump's threats to impose 25% tariffs on Mexico and Canada have left many cities along Mexico's northern border in limbo