President Donald Trump says he told the U.S. military mobilizing at the Southwest border that if migrants try to throw rocks at them, the troops should act as though the rocks are “rifles.”

Trump made the comments Thursday in a speech on immigration. He promised an executive order sometime next week that would ban migrants from claiming asylum if they cross the border illegally, and would set up vast tent cities that would hold anyone coming over the border.

U.S. immigration laws say migrants seeking asylum can do so no matter how they arrive at the U.S.

Several caravans of migrants from Central America are slowly winding north. One group got into a violent confrontation with Mexican police at the border with Guatemala, throwing rocks.