British Prime Minister Theresa May, U.S. President Trump and NATO Secretary-General Jens Stoltenberg listen to Belgian Prime Minister Charles Michel speak during a NATO summit in Brussels on May 25, 2017.

British Prime Minister Theresa May, U.S. President Trump and NATO Secretary-General Jens Stoltenberg listen to Belgian Prime Minister Charles Michel speak during a NATO summit in Brussels on May 25, 2017.