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.

A line of Mexican National Guard and Army trucks rumbled along the border separating Ciudad Juárez and El Paso, Texas Wednesday, among the first of 10,000 officers Mexico has sent to its northern frontier following tariff threats by President Donald Trump.

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Trump has also threatened to introduce tariffs - a tax on imports - on goods from Canada and Mexico, but paused these for 30 days after both countries agreed to boost border security. The US president has said tariffs are needed to help the American economy and to "protect" the country from the "major threat of illegal aliens and deadly drugs".

STORY: Mexican soldiers were mobilized to the U.S. border on Tuesday to crack down on fentanyl trafficking.It's part of a deal between U.S. President Donald Trump and Mexico’s leader Claudia Sheinbaum to pause his threat of tariffs for a month.