
U.S. Secretary of Defense James Mattis (1st R) speaks during a meeting with Ukrainian President Petro Poroshenko (not in the picture) at the Pentagon in Washington D.C., the United States, on June 20, 2017. (Xinhua/Ting Shen)

U.S. Secretary of Defense James Mattis (1st R) speaks during a meeting with Ukrainian President Petro Poroshenko (not in the picture) at the Pentagon in Washington D.C., the United States, on June 20, 2017. (Xinhua/Ting Shen)