British Prime Minister Theresa May addresses the United Nations General Assembly in the Manhattan borough of New York, U.S. September 20, 2016. REUTERS/Eduardo Munoz

British Prime Minister Theresa May addresses the United Nations General Assembly in the Manhattan borough of New York, U.S. September 20, 2016. REUTERS/Eduardo Munoz

British Prime Minister Theresa May addresses the 71st United Nations General Assembly in Manhattan, New York, U.S. September 20, 2016. REUTERS/Carlo Allegri

British Prime Minister Theresa May looks over toward U.S. President Barack Obama as he greets Colombian President Juan Manuel Santos (L) during the luncheon at the United Nations General Assembly in New York September 20, 2016. REUTERS/Kevin Lamarque

U.S. President Barack Obama (R) greets British Prime Minister Theresa May as he arrives for a luncheon during the United Nations General Assembly at United Nations headquarters in New York City, U.S. September 20, 2016. REUTERS/Lucas Jackson

British Prime Minister Theresa May is shown on a large screen as she addresses the 71st United Nations General Assembly in Manhattan, New York, U.S. September 20, 2016. REUTERS/Carlo Allegri

British Prime Minister Theresa May arrives for a luncheon during the United Nations General Assembly at United Nations headquarters in New York City, U.S. September 20, 2016. REUTERS/Lucas Jackson

A car is filled with gasoline at a gas station pump in Carlsbad, California August 4, 2015. REUTERS/Mike Blake