WASHINGTON >> President Donald Trump said today the U.S. would begin “cutting off, or substantially reducing” aid to three Central American nations over a migrant caravan heading to the U.S. southern border.

Trump tweeted: “Guatemala, Honduras and El Salvador were not able to do the job of stopping people from leaving their country and coming illegally to the U.S.”

The three countries received a combined more than $500 million in funding from the U.S. in fiscal year 2017, though it was not immediately clear how much Trump is seeking to cut.

The tweets this morning marked the latest escalation by the president, who is seeking to re-inject immigration politics into the national conversation in the closing weeks of the midterm elections.

On a three-day campaign swing to Western states last week, Trump raised alarm over thousands of migrants traveling through Mexico to the U.S. and threatened to seal off the U.S.-Mexico border if they weren’t stopped.

As the migrants continued their northward march about 900 miles from the U.S. border, Trump tweeted that, “Sadly, it looks like Mexico’s Police and Military are unable to stop the Caravan.

He added: “I have alerted Border Patrol and Military that this is a National Emergy.” White House officials could not immediately provide details.

A Pentagon spokesman, Army Lt. Col. Jamie Davis, said the Pentagon has received no new orders to provide troops for border security.