U.S. President Barack Obama (R) shakes hands with Prime Minister of Singapore Lee Hsien Loong during a joint press conference 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)