BRUSSELS - European Union leaders will be looking to boost aid to Greece as the Balkan migrant route is effectively sealed, using Monday's summit as an attempt to restore unity among the 28 member nations after months of increasing bickering and go-it-alone policies, according to a draft statement Sunday.

The leaders will also try to persuade Turkey's prime minister to slow the flow of migrants travelling to Europe and take back thousands who don't qualify for asylum.

In a draft summit statement produced Sunday and seen by The Associated Press, the EU leaders will conclude that "irregular flows of migrants along the Western Balkans route are coming to an end; this route is now closed." Because of this, the statement added that "the EU will stand by Greece in this difficult moment and will do its utmost to help manage the situation."

"This is a collective EU responsibility requiring fast and efficient mobilization," it said in a clear commitment to end the bickering. It said that aid to Greece should centre on urgent humanitarian aid as well as managing its borders and making sure that migrants not in need of international protections are quickly returned to Turkey.

The statement will be assessed by the 28 leaders after they have met with Turkish Prime Minister Ahmet Davutoglu.

Late Sunday evening, German Chancellor Angela Merkel and Dutch Premier Mark Rutte met with Davutoglu to prepare for the summit.

At least 25 migrants drowned off the Turkish coast while trying to reach Greece on Sunday, Turkey's state-run news agency reported. The coast guard launched a search-and-rescue mission for other migrants believed to be missing in the disaster.

Ankara is central to easing Europe's refugee pressures. More than 2,000 people arrive daily from Turkey to Greece, where many have been stranded as countries on the main migrant route through the Balkans are aiming to stop them moving north.

The bloc has offered several sweeteners to get Turkish authorities to crack down on migrant movements. Some 3 billion euros ($3.3 billion) will be made available for Syrian refugees. Turkey's long-coveted EU membership process is being sped up, as are moves to ease EU visa requirements. Summit meetings like these are also part of the package.

Ahead of the summit, the European Commission trumpeted the availability of tens of millions of euros to help Syrian school children and provide food aid. It said that a new "road map" on visa liberalization for Turkey had also been submitted.

However, Turkey has a huge migrant challenge of its own, as host to more than 2 million people who fled the conflict in Syria, and the returns on the European investments have been limited so far. Many complain that still far too many people cross the Aegean Sea from Turkey to Greece, adding to the 850,000 people who entered Greece that way last year.

The United Nations' refugee agency called on Friday for 400,000 Syrians in Turkey to be resettled around the world to ease the country's burden. So far it remains to be seen if any countries are willing to offer their assistance. Only 7,500 people were resettled in 2015.

After regular calls for Ankara to do more, the Commission announced on Tuesday that Greece was finally in the process of returning 308 migrants not in need of international protection to Turkey.

NATO is helping too. The alliance announced Sunday that it was expanding its mission to help choke off the smuggling of migrants into Europe by deploying warships in Greek and Turkish waters, reinforcing its flotilla and deepening co-operation with the EU's Frontex border agency.

NATO Secretary-General Jens Stoltenberg said in a phone interview with The Associated Press that the alliance "will do reconnaissance, we will do surveillance, we will collect information, and share this information in real time with the Turkish coast guard, the Greek coast guard and with Frontex, helping them with managing the migrant and refugee crisis, and also to cut the lines of the illegal trafficking and smugglers," Stoltenberg said.

The EU summit, the second of three in Brussels in just over a month, comes just days after a Turkish court ordered the seizure of the opposition Zaman newspaper. The move has heightened fears over deteriorating media freedom in the country and led to calls for action from the international community, but they will most likely be brushed aside at the high-stakes talks.

"In other words, we are accepting a deal to return migrants to a country which imprisons journalists, attacks civil liberties, and with a highly worrying human rights situation," said Guy Verhofstadt, leader of the ALDE liberal group in the European Parliament on Sunday.

The summit will centre on an appeal for unity and for countries to implement several migrant policy measures they've already agreed to. In the Balkans, Slovenia, Croatia and Hungary - with support from Austria - have encouraged Macedonia to squeeze its border with Greece, allowing only a trickle of people onto its territory.

Many of the preferred destinations for migrants, like Germany and Scandinavia, have reintroduced border controls, threatening the future of the Schengen passport-free area so vital to trade and travel. Croatia signalled Friday that it's ready to deploy the army.

Ahead of the summit, between 13,000 and 14,000 were camped at the Greek-Macedonia border, clinging to the hope that they might be allowed to move north.

Ravaged by a massive debt crisis, Greece has neither the resources nor the capacity to process and shelter people. Last Wednesday, the European Commission proposed to earmark 700 million euros ($760 million) in humanitarian aid to deal with the refugee crisis in Greece and along the Balkan route.