A deal between the European Union and Turkey meant to curb the flow of migrants into Europe in return for financial and political rewards could unravel within months because neither side looks able to deliver on its commitments.

Turkish Prime Minister Ahmet Davutoglu and European Council President Donald Tusk wore relieved smiles Friday as they sealed a pact for Ankara to take back all migrants and refugees who cross to Greece in exchange for more money, faster visa-free travel for Turks and slightly accelerated EU membership talks.

But for Turkey to halt the flow of migrants to Europe will require a major redeployment of its security apparatus to shut down a lucrative people-smuggling business at a time when President Recep Tayyip Erdogan has more pressing priorities.