[Czech Republic's PM Sobotka arrives at the EU-Turkey summit in Brussels]By Jan Lopatka PRAGUE (Reuters) - Central European leaders are ready to help Balkan countries seal their borders with Greece to stem the flow of migrants across the continent, Czech Prime Minister told Reuters on Sunday. Despite objections from regional powerhouse Germany, which says it would make the situation in Greece more difficult, the so-called Visegrad group will debate the plans on Monday at a summit hosted by Sobotka.