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

Trump tweets: “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.”

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. We will now begin cutting off, or substantially reducing, the massive foreign aid routinely given to them. — Donald J. Trump (@realDonaldTrump) October 22, 2018

The three countries received a combined more than $500 million in funding from the U.S. in fiscal year 2017.

Trump has raised alarm over thousands of migrants traveling through Mexico to the U.S., saying, “Sadly, it looks like Mexico’s Police and Military are unable to stop the Caravan.”

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