Lilian Tintori (C), wife of jailed Venezuelan opposition leader Leopoldo Lopez takes part in a rally to demand a referendum to remove Venezuela's President Nicolas Maduro, in Caracas, Venezuela, September 16, 2016. REUTERS/Henry Romero

(L-R) Ireland's Prime Minister Enda Kenny, Cyprus' President Nicos Anastasiades , Denmark's Prime Minister Lars Lokke Rasmussen, Germany's Chancellor Angela Merkel, Belgian Prime Minister Charles Michel and Italy?s Prime Minister Matteo Renzi attend the European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 16, 2016. REUTERS/Yves Herman

European Union leaders pose for a family photo during the European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 16, 2016. REUTERS/Leonhard Foeger

Hungary's Prime Minister Victor Orban (L), Germany's Chancellor Angela Merkel and Austria's Chancellor Christian Kern (R) arrive to pose for a family photo during the European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 16, 2016. REUTERS/Leonhard Foeger

European Parliament President Martin Schulz (L) is welcomed by Slovakia's Prime Minister Robert Fico at the Government office ahead of the upcoming European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 15, 2016. REUTERS/Yves Herman

EU leaders attend the European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 16, 2016. REUTERS/Yves Herman

European Council President Donald Tusk (3rdL), European Commission President Jean-Claude Juncker (2ndR) and European Parliament President Martin Schulz (L) pose for a group photo with Slovakia's Prime Minister Robert Fico (C), Slovakia's President Andrej Kiska (3rdR) and Speaker of the Slovakia's National Council Andrej Danko (2ndL) at the Government office ahead of the upcoming European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 15, 2016. REUTERS/Yves Herman

European Union countries flags are seen at the Bratislava Castle (Hrad) during the European Union summit- the first one since Britain voted to quit- in Bratislava, Slovakia, September 16, 2016. REUTERS/Yves Herman