U.S. Marines place concertina wire at the Otay Mesa Port of Entry in California on Nov. 11, 2018.

WASHINGTON — The Pentagon estimates that the cost of the 5,900 troops deployed to the southwest border will total $72 million, spokesman U.S. Army Col. Rob Manning said in a statement Monday.

The cost estimate from the Pentagon comes two weeks after CNBC learned that the deployment was shaping up to have a price tag of $220 million and that the caravan did not pose a threat to the United States, according to sources with direct knowledge of a U.S. intelligence assessment.

Last month, Defense Secretary James Mattis approved the deployment of thousands of active-duty troops from across the United States to help "harden" the southwestern border in response to a caravan of migrants from Central America.

In mid-October, a caravan of at least 3,500 Central American migrants seeking asylum left Honduras for the United States border.

President Donald Trump made the caravan of Central American migrants one of his prime targets ahead of midterm elections. The president has referred to the caravan as an "invasion" while claiming that Democrats want open borders, which Democrats deny.

The movement of thousands of active-duty troops to the border has been criticized as a political stunt designed to back Trump's campaign promise of securing U.S. ports of entry.

Mattis downplayed that criticism last month saying that Pentagon is providing "practical support based on the request from the commissioner of customs and border police."

"We don't do stunts in this department," he added at the time.

The Department of Defense originally estimated that more than 7,000 troops would take positions in California, Arizona and Texas in support of the Department of Homeland Security and Customs and Border Protection. In which case, the border mission, will have a larger U.S. military footprint than the combined efforts in Iraq and Syria.

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