HAVANA, June 5, 2016 (Xinhua) -- Cuban President Raul Castro (front C) poses for group photos with guests during the opening ceremony of a summit of the Association of Caribbean States (ACS) in Havana, capital of Cuba, on June 4, 2016. Presidents and heads of state of the Association of Caribbean States (ACS) met here on Saturday to push up economic and political cooperation in tackling regional challenges. (Xinhua/Liu Bin)