Barack Obama, Matteo Renzi, Angela Merkel, Francois Hollande, David Cameron, Petro Poroshenko

President Barack Obama poses for a photo with, from left, Italian Prime Minister Matteo Renzi, British Prime Minister David Cameron, Ukrainian President Petro Poroshenko, German Chancellor Angela Merkel, and French President Francois Hollande, at PGE National Stadium in Warsaw, Poland, Saturday, July 9, 2016. (AP Photo/Susan Walsh)

President Barack Obama poses for a photo with, from left, Italian Prime Minister Matteo Renzi, British Prime Minister David Cameron, Ukrainian President Petro Poroshenko, German Chancellor Angela Merkel, and French President Francois Hollande, at PGE National Stadium in Warsaw, Poland, Saturday, July 9, 2016. (AP Photo/Susan Walsh)