Last year, more than a million entered the EU by boat, mostly travelling from Turkey to Greece, with 13,000 people currently stuck on Greece's border with Macedonia.
The EU has pledged €3bn (£2.3bn) to Turkey in return for housing migrants and stemming the flow.
Yet, the EU wants Turkey to keep its border with Syria open to refugees, but to close its border to Greece and also wants it to accept non-Syrian migrants that Europe turns back from the EU.
In that vein, the 28 EU member states are anticipated to request that Turkey take back thousands of migrants who don't qualify for asylum, hoping to close the Balkan route for migrants.
While European Council President Donald Tusk has said he had been told by Turkish President Recep Tayyip Erdogan that his country would be willing to take back all migrants apprehended in Turkish waters, the move means that the EU is relying on Turkey at the same time that it is apprehensive about some of its actions.
Meanwhile, Prime Minister David Cameron has announced the UK military will join Nato forces intercepting and returning migrants to reach Europe From Turkey.
Cameron said the UK will be deploying the amphibious landing ship RFA Mounts Bay in the Aegean Sea.
Increased tensions between Turkey and Russia in Syria following the shooting down of a Russian aircraft last year by Turkey, after the aircraft briefly stayed into Turkish airspace, have made some leaders nervous given that Turkey is a member of Nato. As Turkey is a member of Nato it could hypothetically invoke the alliance’s collective defence treaty.
The Turkish government also seized an opposition newspaper on Friday. Zaman newspaper printed a pro-government edition on Sunday, its first edition printed under new management. The EU issued a statement of concern following the raid.
Yet, with more than 2,000 migrants arriving daily in Greece from Turkey, the EU doesn't have too much choice, and it is expected leaders will play down these concerns.