[A migrant pushes a wheelbarrow in a muddy field at a camp of makeshift shelters called the Grande Synthe jungle, near Calais]By Robin Emmott AMSTERDAM (Reuters) - Europe needs Turkey to dramatically cut the number of migrants reaching Greece within weeks or the pressure for more border closures and fences will grow, the EU's top official in charge of ties with Ankara warned on Saturday. Frustrated that refugees continue to stream into Greece despite a Nov. 29 deal between Ankara and Brussels to slow down the flows, European Commissioner Johannes Hahn said Turkey must show results by the time EU leaders meet for a Feb. 18-19 summit. "This action plan was agreed more than two months ago and we are still not seeing a significant decline in the number of migrants," Hahn, the EU's enlargement commissioner, told Reuters after an EU foreign ministers' meeting in Amsterdam attended by Turkey's foreign minister, Mevlut Cavusoglu.