HO CHI MINH CITY, Vietnam (Reuters) - U.S. Defense Secretary Jim Mattis said President Donald Trump has reassured him of his full support after the Republican president described his Pentagon chief as “sort of a Democrat” who could leave the administration. FILE PHOTO: U.S. President Donald Trump walks in with U.S. Defense Secretary Jim Mattis as they arrive to attend the multilateral meeting of the North Atlantic Council in Brussels, Belgium July 11, 2018.