French President Francois Hollande (L) and German Chancellor Angela Merkel deliver a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / JOE KLAMARJOE KLAMAR/AFP/Getty Images

(L to R) Slovakia's Prime minister Robert Fico, President of the European Council Donald Tusk and European Commission President Jean-Claude Juncker deliver a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / StringerSTRINGER/AFP/Getty Images

Hungarian Prime Minister Viktor Orban arrives for the press conference after European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / VLADIMIR SIMICEKVLADIMIR SIMICEK/AFP/Getty Images

President of the European Commission Jean-Claude Juncker (R) and European Council President Donald Tusk deliver a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / StringerSTRINGER/AFP/Getty Images

French President Francois Hollande delivers a joint statement with the German Chancellor after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / JOE KLAMARJOE KLAMAR/AFP/Getty Images

French President Francois Hollande (L) and German Chancellor Angela Merkel deliver a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / JOE KLAMARJOE KLAMAR/AFP/Getty Images

Hungarian Prime Minister Viktor Orban attends a press conference after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / VLADIMIR SIMICEKVLADIMIR SIMICEK/AFP/Getty Images

French President Francois Hollande (R) and German Chancellor Angela Merkel arrive to deliver a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / STEPHANE DE SAKUTINSTEPHANE DE SAKUTIN/AFP/Getty Images