WASHINGTON, DC - APRIL 01: (L-R) U.S. President Barack Obama talks to National Security Adviser Susan Rice as Prime Minister of the United Kingdom David Cameron looks on during a scenario-based policy discussion of the 2016 Nuclear Security Summit April 1, 2016 in Washington, DC. U.S. President Barack Obama is hosting the fourth and final in a series of summits to highlight accomplishments and make new commitments towards reducing the threat of nuclear terrorism. (Alex Wong/Getty Images)
{"Image Copyright": "2016 Getty Images"}