ANKARA/BRUSSELS (AFP) - At least 18 people drowned trying to cross the Aegean Sea on Sunday (March 6), on the eve of a key summit at which European leaders will push Turkey to accept "large-scale" deportations of economic migrants from Greece.

The International Organization for Migration said before the latest tragedy that a total of 418 people have died or gone missing already in 2016, most while attempting to reach Greece from Turkey aboard unseaworthy boats.

The European Union's 28 leaders are hoping for more cooperation from Turkish Prime Minister Ahmet Davutoglu at their talks in Brussels on Monday in order to slow the flow from Turkey to Greece, the main entry point to Europe.

A Turkish official said that at least 18 migrants perished on Sunday in an all too familiar fashion, after their boat capsized in the Aegean while trying to cross to Greece. Fifteen migrants were rescued from the boat off the coastal town of Didim.

Turkey is the launch pad for most of the more than one million refugees and migrants who have come to the continent since early 2015.

On Saturday, European Migration Commissioner Dimitris Avramapoulos said Greece - already struggling with a buildup of 30,000 migrants - was expected to receive "another 100,000" by the end of March.

EU leaders will also try to increase aid for Greece which has seen non-EU Macedonia and EU countries on the western Balkans route virtually close their borders, trapping asylum seekers desperate to head north to wealthy Germany and Scandinavia.

Macedonia allowed just 240 people to cross the border with Greece between Saturday and early Sunday morning, Greek frontier police said.

Donald Tusk, the European Council president and summit host, said in his invitation letter that success depended largely on securing Turkey's agreement at the talks for the "large-scale" readmission from Greece of economic migrants who do not qualify as refugees.

Syrians, who top the influx of people into Europe, are considered genuine refugees requiring admission under international law.

Brussels has meanwhile unveiled a plan for saving Europe's passport-free Schengen zone, which has been jeopardised by several countries closing their borders to stop the huge influx of people.

"For the first time since the beginning of the migration crisis, I can see a European consensus emerging," Tusk said in his letter.

In preparation for the summit, Davutoglu was to meet late Sunday with Chancellor Angela Merkel and Prime Minister Mark Rutte of the Netherlands, which holds the current rotating EU presidency, a diplomat told AFP.

Following their lunch Monday with Davutoglu in Brussels, EU leaders are to meet by themselves.

The EU said Turkey has made progress toward implementing a cooperation-for-aid deal clinched in November but added that too many people were still heading from Turkey to Greece, with nearly 2,000 arriving daily in February, a winter month.

In a report to EU summit participants the European Commission, the EU executive, said encouragingly that Ankara late last month approved 859 readmission requests from Greece.

If Turkey substantially reduces the migrant flow, Rutte has said, Europe could implement a more "ambitious" plan to resettle refugees directly from camps in Turkey, which already host 2.7 million Syrian refugees.

Under the action plan, the EU will give Turkey three billion euros (S$4.5 billion) to aid refugees on its territory and Turkey will crack down on people smugglers.

In its report, the commission urged Turkey to "take decisive action against migrant smuggling" by stepping up police work, coast guard patrols and cooperation with NATO.

Turkey on Wednesday denied claims it was blocking Nato vessels deployed in the Aegean Sea from launching a new anti-smuggling mission.

Under their deal, Turkey expects to accelerate its bid for EU membership and see Brussels ease visa requirements for Turks visiting the Schengen area.

Lingering tensions between Brussels and Ankara flared when Turkish police seized an opposition newspaper at the weekend and Brussels warned Ankara it had to respect media freedom in its decade-long bid for EU membership.

In a bid to ease pressure on Greece, EU leaders will urge member states to "accelerate relocation" of Syrians, Iraqis and Eritreans from the frontline state, according to summit draft.

Since adopting a scheme last September to relocate 160,000 such asylum seekers from Greece as well as Italy, European Union countries have taken in just 660 people, according to EU figures.

Merkel - whose country has admitted the most asylum seekers by far in Europe - said Greece should have been quicker to provide lodgings to host 50,000 people under an agreement with the EU in October.