Can Turkey stop the flow of migrants into Europe?
Turkish President Recep Tayyip Erdogan is in Brussels to discuss the migration crisis with EU leaders.
Turkey has become the key to stopping the hundreds of thousands of migrants and refugees trying to cross into Europe.
But with two million Syrians now in Turkey and most living in the big cities, not refugee camps, it will be extremely tough to halt the flow.
The BBC's Istanbul correspondent, Mark Lowen reports.