U.S. President Barack Obama speaks during a joint press conference with Prime Minister of Singapore Lee Hsien Loong (not seen) at White House in Washington D.C., capital of the United States, Aug. 2, 2016. At the invitation of U.S. President Barack Obama, Singapore Prime Minister Lee Hsien Loong made an official visit to the White House on Tuesday to celebrate the 50th anniversary of diplomatic relations between the two countries. (Xinhua/Bao Dandan)