Turkey has blocked its land border with Greece but thousands of migrants and refugees leave by sea every day
"Money is not the big problem," admitted European Council President Donald Tusk. "This is not as easy as expected."
He was talking about Turkey.
And if one thing became clear at this week's emergency EU summit, it was that Turkey is rapidly emerging as the key ally Europe needs, if it is to have any hope of stemming the vast flow of refugees and migrants on to European soil.
You only need to glance at a map to know that a country long described as the bridge between East and West has now become the bridge between the Syrian civil war and the European Union.
And the narrow sea lanes between Turkey's Aegean coast and the Greek islands have become the EU's most porous border.
So can anything be done to change that, and what does Turkey want in return?
Well, so far, money is precisely what is on offer from Brussels - the European Commission has proposed giving €1bn (£700m; $1.1bn) to help the Turks deal with the consequences of having an estimated two million Syrian refugees on its territory.
Turkey also figures prominently in the summit conclusions, external, and German Chancellor Angela Merkel went out of her way to emphasise the huge challenge Turkey faces.
"We must make sure that (aid) programmes there are properly financed," she said, "and that we can jointly maintain better security at the borders."
EU leaders avoid punch-up but fail refugee test
Ambitious goals
But Turkey wants more than just money. The government says it has already spent nearly €7bn looking after Syrian refugees, so another billion from Europe is hardly a game-changer.
The goals of the government in Ankara are more ambitious.
In a long letter sent to all EU leaders at the summit, Turkish Prime Minister Ahmet Davutoglu set out proposals for a buffer zone - and a no fly zone - stretching for 80km (50 miles) in northern Syria.
If it could be made safe, the letter suggested, it could be used as an area for the "voluntary return of refugees".
Ahmet Davutoglu says his country is determined to set up a safe zone just across the border in northern Syria
Or to put it another way, if you don't want them all heading west towards Europe, how about helping us send them back east, into a safe zone in Syria?
At first sight it might sound like a viable solution. But it is fraught with danger, difficulty and geopolitical complications.
Turkey has floated the idea before, and it may see the current migration crisis as another opportunity to press its case.
But the Turks also want the buffer zone to split Kurdish militias fighting against the Islamic State group in Syria, from Kurdish PKK rebels fighting against the security forces in south-eastern Turkey.
Visa requirements
In the circumstances, it is hardly surprisingly that there is little enthusiasm for the idea in the EU.
So what else could Turkey get in return for greater co-operation on the refugee issue?
Turkey says it needs help to cope with the refugees arriving from Syria
One potential carrot is progress on visa liberalisation - with the eventual goal of lifting visa requirements for Turkish citizens travelling to Europe.
"That is certainly on offer," one official in Brussels said, although some countries would be more hesitant than others.
All of this will be the subject of a series of high-level meetings in the coming weeks.
Angela Merkel will meet PM Davutoglu at the UN General Assembly in New York next week, and then Turkey's powerful President, Tayyip Erdogan, will travel to Brussels for a mini-summit with the presidents of the European Council and the European Commission.
"There could be some robust conversations," said one senior EU official. "And if the Turks refuse to play ball we will have to think again."
Off course
EU officials think Turkey is not doing enough to crack down on the profitable business of smuggling people across the Aegean to Greece.
Migrants reaching the shores of Lesbos in recent weeks have relied on the help of smugglers on the Turkish coast
But Mr Erdogan will argue that Turkey has been shouldering the burden of Syrian refugees on its own for far too long.
It does not help matters that relations between Ankara and Brussels are often strained.
Turkey's negotiations on future EU membership have drifted off course, and President Erdogan has been criticised recently on a range of issues, from press freedom to what his critics see as his increasingly autocratic tendencies.
But now the EU needs him more than ever, as it faces up to the scale of the refugee crisis.
And one thing can be guaranteed - Mr Erdogan will strike a hard bargain.
