The European Union is in the midst of negotiating a complex deal with Turkey aimed at ending migration flows across the Aegean Sea and into the bloc.
EU leaders must first agree on a common position among all 28 before sitting down on Friday with Turkish Prime Minister Ahmet Davutoglu to hammer out a deal.
Many of them have hesitations about the proposed plan, which centres on a legally challenging migrant swap deal with Turkey and closer ties between Ankara and the EU.
Here is what leaders had to say ahead of their summit:
EU PRESIDENT DONALD TUSK:
"I am cautiously optimistic, but frankly speaking more cautious than optimistic [of reaching a deal]."
AUSTRIAN CHANCELLOR WERNER FAYMANN:
"The alternative [to a deal with Turkey] is quickly explained: Everyone travels wherever they want, without limit. If you want the alternative, then I say: No."
GERMAN CHANCELLOR ANGELA MERKEL:
"We need to find a balance of interests between the EU member states and Turkey. ... I think it is within the realm of the possible - I am consciously careful - for us to find such a common position."
BRITISH PRIME MINISTER DAVID CAMERON:
"If we can get an agreement that returned migrants from the Greek islands to Turkey, that would be good progress."
DUTCH PRIME MINISTER MARK RUTTE:
"It is crucial we get a deal. If we don't, the crisis continues and people continue to drown; Greece will fill up with refugees who cannot get through."
ESTONIAN PRIME MINISTER TAAVI ROIVAS:
"We are here to seal the deal with Turkey. ... We do understand this is quite a Herculean task we have, but we need to make it work."
LITHUANIAN PRESIDENT DALIA GRYBAUSKAITE:
"I think that the proposed package is very complicated, will be very difficult to implement and it is on the edge of international law."
LUXEMBOURG PRIME MINISTER XAVIER BETTEL:
"You know I have fears concerning the legal aspect of it all. I have been given assurances but I am still not convinced. ... I do not want a judge to tell us in a few weeks' time that we were wrong from start to finish."
BELGIAN PRIME MINISTER CHARLES MICHEL:
"I prefer no agreement at all rather than a bad agreement. ... Turkey is effectively demanding a lot. And I don't accept negotiations that sometimes resemble a form of blackmail."
CYPRIOT PRESIDENT NICOS ANASTASIADES:
"If Turkey will fulfill its obligations according to the Ankara Protocol and the [EU-Turkey] negotiating framework, then there is no problem. But without it, we could do nothing."