WASHINGTON (AP) -- President Donald Trump says he wants to use the military to secure the U.S.-Mexico border until his promised wall is built.

Trump said Tuesday during a lunch with Baltic leaders that he's spoken with Defense Secretary Jim Mattis about the idea.

Trump said, "We're going to be doing things militarily until we can have a wall and proper security." He's calling it a "big step."

Trump begrudgingly signed a spending bill last month that provided far less money for the wall than he wanted. He's been complaining that U.S. borders are too porous and its immigration laws are too weak.

Trump administration officials say they're crafting a new legislative package aimed at closing immigration "loopholes" following the president's calls for Republican lawmakers to immediately pass a border bill.

In one of his many tweets on Monday, Trump wrote, "Honduras, Mexico and many other countries that the U.S. is very generous to, sends many of their people to our country through our WEAK IMMIGRATION POLICIES." In another, he wrote in all caps, "ACT CONGRESS!"

Trump has been seething over immigration since realizing the major spending bill he signed last month barely funds the "big, beautiful" border wall he has promised his supporters.

Among the measures the administration is pursuing is ending special safeguards that prevent the immediate deportation of children arrested at the border and traveling alone.

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