Donald Tusk (C), President of the European Council, shakes hands with with UN Secretary-General Ban Ki-moon, as Frans Timmermans, First Vice-President of the European Commission looks on at the United Nations Headquarters, September 18, 2016, in New York City. / AFP PHOTO / DOMINICK REUTERDOMINICK REUTER/AFP/Getty Images

Donald Tusk, President of the European Council, and Frans Timmermans, First Vice-President of the European Commission, meet with UN Secretary-General Ban Ki-moon at the United Nations Headquarters, September 18, 2016, in New York City. / AFP PHOTO / DOMINICK REUTERDOMINICK REUTER/AFP/Getty Images

Donald Tusk (L), President of the European Council, arrives with UN Secretary-General Ban Ki-moon for a meeting at the United Nations Headquarters, September 18, 2016, in New York City. / AFP PHOTO / DOMINICK REUTERDOMINICK REUTER/AFP/Getty Images

Federal Bureau of Investigation (FBI) officials label and collect evidence near the site of an explosion which took place on Saturday night in the Chelsea neighborhood of Manhattan, New York, U.S. September 18, 2016. REUTERS/Rashid Umar Abbasi

With New York Governor Andrew Cuomo alongside, New York Mayor Bill de Blasio, seen here shaking hands with a policeman, surveys the site of an explosion which occurred in the Chelsea neighborhood of New York, U.S., September 18, 2016. REUTERS/Rashid Umar Abbasi

A view of a mangled dumpster at the site of an explosion that occurred on Saturday night in the Chelsea neighborhood of New York, USA, September 18, 2016. REUTERS/Justin Lane/Pool

Minister of Foreign Affairs Yun Byung-se of South Korea speaks during a meeting between leaders from South Korea, Japan and the United States in New York, U.S. September 18, 2016. REUTERS/Kevin Hagen/POOL

U.S. Secretary of State John Kerry speaks during a meeting with the Republic of Korea and Japan in New York, U.S. September 18, 2016. REUTERS/Kevin Hagen/POOL