WASHINGTON — President Trump said on Tuesday that he planned to order the military to guard parts of the southern border until he can build a wall and tighten immigration restrictions, proposing a remarkable escalation of his efforts to crack down on migrants entering the country illegally.

Mr. Trump, who has been stewing publicly for days about what he characterizes as lax immigration laws and the potential for an influx of Central American migrants to stream into the United States, said he had been discussing with Jim Mattis, the secretary of defense, about resorting to military deployments.

“We have very bad laws for our border, and we are going to be doing some things — I’ve been speaking with General Mattis — we’re going to be doing things militarily,” Mr. Trump said at the White House, seated beside the defense secretary at a meeting with visiting leaders of Baltic nations. “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. We really haven’t done that before, or certainly not very much before.”

Mr. Trump’s comments came after he kicked off his third consecutive day of tweeting about America’s “weak” border laws on Tuesday and called on Congress to act, following a new push for legislation to enforce immigration laws for those living illegally in the United States.

Trump Says He Plans To Order Military To Guard Border, By Julie Hirschfeld Davis And Eileen Sullivan, April 3, 2018