President Donald Trump said Tuesday he’s preparing to deploy the military to the United States’ southern border, in the latest escalation of Trump’s campaign to win funding for an expanded U.S.-Mexico border wall.

President Donald Trump: “We are going to be doing some things. I’ve been speaking with General Mattis. We’re going to be doing things militarily, until we can have a wall and proper security. We’re going to be guarding our border with the military. That’s a big step.”

Trump has offered few details on how such a plan would be implemented. Presidents Obama and George W. Bush both deployed National Guard troops to the Mexican border to assist the U.S. Border Patrol. An 1878 law known as the Posse Comitatus Act bars the military from carrying out law enforcement actions inside the United States.