By Jan Lopatka and Robert Muller PRAGUE (Reuters) - The European Union must provide support to western Balkan countries outside the bloc to help them halt the flow of migrants north from Greece towards the heart of the EU, Czech Prime Minister Bohuslav Sobotka said on Thursday. In an interview with Reuters, Sobotka hailed steps by western Balkan nations to stop an uncontrolled influx into the EU via their territory of people fleeing from war or failed states across the Middle East and Africa. "Today the situation is that countries in the western Balkans are willing to regulate migration and Europe must unequivocally support them in that," he said in an interview.