PALM BEACH: President Donald Trump is threatening to close the U.S. border with Mexico for an undisclosed period of time if his administration determines that its southern ally has lost "control" on its side. Trump is citing the situation involving migrants camped in Tijuana, Mexico, after traveling in a caravan to reach the United States. Trump calls it "a really bad situation" there and says that "if we find that it"s incontrollable," then "we will close entry into the country for period of time until we can get it under control. The whole border." The president also says he"s given American troops at the border the "OK" to use lethal force against migrants "if they have to." Trump tells reporters: "I hope they don"t have to," but he says, "I have no choice" because "you"re dealing with rough people."