The US will deploy up to 5,000 active-duty troops to the U.S.-Mexico border in an effort to prevent members of a migrant caravan from illegally entering the country, a U.S. official said Monday.

The new figure is a major increase from initial estimates of 800 troops and would represent a military force equal to about one-third the number of customs officials currently working at the border. The military sent about 2,000 National Guard troops to the area earlier this year, reported by WSJ

Administration officials said last week that they were considering a plan to send up to 1,000 active duty troops to the border, but that deployment has increased to 5,000, one Department of Homeland Security official told USA Today.

In recent weeks, the president has been warning repeatedly about the dangers posed by a caravan of mostly Central American migrants, which has swelled to an estimated 7,000 people and is continuing its slow trek north through Mexico.

The U.S. and federal law-enforcement officials said troops are likely to be deployed to ports of entry, at least in initial phases of the U.S. military mission, which the Pentagon has named Operation Faithful Patriot.

U.S. troops later expect to support border officials by doing things like building tents, providing medical support and helping staff command and control centers.

Under the latest plans, about 1,800 troops will go to Texas, 1,700 to Arizona and 1,500 to California. The troops will be drawn from about 10 U.S. Army installations and consist largely of military police and engineers, one of the U.S. officials said. U.S. Marines also will be deployed, the U.S. official said.

President Trump has vowed that the migrants won’t be allowed into the country, calling the movement a “national emergency.”

Last week, he told the group to “turnaround” and “go back to your Country” — a plea he repeated in a tweet Monday.

“Many Gang Members and some very bad people are mixed into the Caravan heading to our Southern Border,” Trump wrote. “Please go back, you will not be admitted into the United States unless you go through the legal process. This is an invasion of our Country and our Military is waiting for you!”

On Sunday, some of caravan stopped to rest in San Pedro Tapanatepec, located in eastern Oaxaca.

A second caravan that recently formed broke through border gates in the Guatemala town of Tecun Uman and clashed with Mexican authorities Sunday, resulting in the death of a 26-year-old Honduran man. He was struck in the head with a rubber bullet and killed.

That same day, 300 migrants left from San Salvador to also begin the long trek north.

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