BRUSSELS - Turkey's prime minister made a new proposal for tackling the migrant crisis at a summit in Brussels on Monday, leading EU leaders to extend their meeting, officials said.

"There is a new proposal. We are trying to open the way to solve this process, that's why this is a new proposal," Prime Minister Ahmet Davutoglu's spokesman told reporters.

He refused to give details of the new offer, but added: "We are not here just to talk about migrants. Of course Turkey's EU accession process is an issue for us here.

"Our partners have good intentions and we have good intentions and all of us want to solve this. We want to find common ground."

European Union leaders called the summit to follow up on a deal signed with Turkey in November, under which Ankara agreed to cut the flow of migrants to Europe and take back more deportees in exchange for three billion euros ($3.3 billion) in aid.

The EU also agreed to open new "chapters" in Turkey's long-stalled bid to join the EU.

Irish Prime Minister Enda Kenny told reporters said he believed that one of the issues Turkey had brought up was speeding up the relaxation of visa regulations for Turkish nationals travelling to Europe.

European sources confirmed that the summit, due to involve a working lunch with Davutoglu followed by a meeting of the 28 EU leaders, had now been extended into the evening. "The Turks are offering more, they are demanding more," a senior European source told AFP. "It's more ambitious on all aspects".

The source added: "Davutoglu has presented some new ideas and new proposals at lunch. The EU 28 will gather at a working session to discuss the new ideas - that will take some time. "Then we have foreseen a dinner with the participation of Davutoglu."

EU leaders expressed guarded optimism before a summit with Turkey on Monday that Ankara was finally ready to act to curb a flood of migrants crossing illegally into Europe.

They also voiced concern, tinged with embarrassment, that increased Turkish cooperation coincides with a crackdown on media freedom that runs counter to cherished European values.

Prime Minister Ahmet Davutoglu said the half-day meeting would also address Ankara's bid to join the European Union and he hoped for a "turning point", adding that Turkey was indispensable for the EU, just as Europe was for Turkey. EU officials said, however, that he arrived with stiff new demands.

With tens of thousands of migrants stranded in Greece by closing borders, the summit may formally declare closed the Balkan route from Greece to Germany, diplomats said, although that is one of several issues where opinion is sharply divided.

Leaders will pledge help to Athens cope with the backlog and seek assurances that Turkey, with NATO naval back-up in the Aegean, will stop people smugglers putting migrants to sea.

"I hope we will make a step forward to achieving these goals today but that will take difficult negotiations so it may take a while to get a result," German Chancellor Angela Merkel said.

Merkel and Dutch Prime Minister Mark Rutte, whose country holds the rotating EU presidency, spent five hours talking with Davutoglu in Brussels until 2:45 a.m. to try to nail down commitments to halt the migrant flow after more than one million people - mostly Syrians, Iraqis and Afghans - entered Europe last year, most ending up in Germany.

"I am sure these challenges will be solved through our cooperation and Turkey is ready to work with the EU," Davutoglu said. "Turkey is ready to be a member of the EU as well. Today I hope this summit will not just focus on irregular migration but also the Turkish accession process to the EU."

EU officials said Davutoglu had raised the stakes, however, by demanding much more EU cash than the 3 billion euros ($3.3 billion) pledged to help the 2.9 million Syrian refugees Turkey is housing, faster moves to negotiate Turkish membership of the EU and an immediate easing of EU visa rules for Turks - something the Europeans have offered only for late in the year.

"The Turks are negotiating very hard," a senior EU diplomat said. Another spoke of alarm that hard bargaining could disrupt talks to reunite Greek- and Turkish-speaking parts of Cyprus.

DIVISIONS

There were also continued divisions among EU leaders, with Merkel resisting a push for a public endorsement by the summit of border closures by Austria and Greece's Balkan neighbours.

Merkel, who faces a possible political backlash against her welcome for the refugees in three regional elections on Sunday, requested the emergency summit to show voters the EU is acting to resolve the crisis.

Her finance minister, Wolfgang Schaeuble, said on Sunday that Berlin had major doubts about whether Turkey should become a member of the EU.

Before the summit, EU officials told Davutoglu of their concerns about human rights after the Turkish government seized control of a critical newspaper, top-selling daily Zaman.

European Parliament President Martin Schulz said he had told the Turkish premier that media freedom was "a non-negotiable element of our European identity" and they had differed sharply. The migrant crisis meant the EU needed to work with Turkey even if it was in "total disagreement" with its policies, he said.

German and Dutch government spokesmen said Merkel and Rutte had also raised press freedom with Davutoglu.

The EU is taking care not to alienate Ankara just as hopes are rising of a solution to the migration problem.

Fellow EU leaders, long divided over how to end chaotic movements that have put Europe's Schengen open border system in jeopardy, will also assure Greek Prime Minister Alexis Tsipras of help housing migrants now stranded in Greece.

Tsipras said the bloc must speed up the process of relocating registered asylum seekers from Greece to other EU countries as promised last September. EU states have so far taken in only a few hundred of a promised 160,000 people.

Summit chairman Donald Tusk proposed an EU endorsement of border closures on the route north from Greece, diplomats said, along with a renewed commitment to revive the relocation plan.

A draft EU statement seen by Reuters said: "Irregular flows of migrants along the Western Balkans route are coming to an end; this route is now closed."

However, negotiations were continuing, officials said.

NATO said on Sunday a new naval force had approval to operate in Turkish and Greek waters. That will lend force to a deal with Turkey to take back migrants halted in its waters and those who reach Greek islands but do not qualify for asylum.

Germany has been pushing for direct resettlement of thousands of Syrian refugees from Turkey. But diplomats say that is unlikely to be discussed in detail by other EU leaders until they see flows from Turkey are falling sharply.

Some 33,000 migrants are bottled up in Greece and about 2,000 more have been arriving daily.

British Prime Minister David Cameron said he was sending a naval force to the Aegean to join German and Canadian warships in the NATO force assisting the Greek and Turkish navies.

Though Britain is outside the Schengen zone, further migrant chaos could damage Cameron's efforts to win a June referendum and keep Britain in the EU.