WASHINGTON (AP) -- US President Donald Trump is suggesting he has left standing orders for the US military to destroy Iran "at levels they've never seen before" if Tehran follows through on its long-standing threats to kill him. But the US government has no way to create an automatic, preauthorized "dead man's switch" that would prompt immediate retaliation. Instead, if Trump were killed, the transfer of power to his successor is governed by the 25th Amendment and the Presidential Succession Act