U.S. President Donald Trump speaks to reporters before departing on a campaign trip on the South Lawn of the White House in Washington, U.S., November 2, 2018. REUTERS/Kevin Lamarque WASHINGTON (Reuters) - President Donald Trump on Friday backtracked from his suggestion a day earlier that U.S. troops sent to the U.S. border with Mexico would be free to fire on migrants who throw rocks at them, saying that rock-throwers would only be arrested. “They won’t have to fire.