EU President Donald Tusk warned Thursday that "difficult" talks lay ahead on a contentious plan being negotiated with Turkey to stem migration flows into Europe, hours before the bloc's leaders were set to meet to forge a common approach.

The plan - under which migrants would be swapped between the European Union and Turkey in a bid to end illegal smuggling across the Aegean Sea to Greece - is the bloc's latest effort to end a surge of migrants and asylum seekers into the continent.

Last year, more than 1 million people reached Europe's shores, with most of them travelling via Turkey to Greece in the hope of reaching wealthy northern states such as Germany and Sweden. Many had fled the war in Syria, but economic migrants joined their ranks.

The EU now hopes that its leaders, together with Turkey, can declare an end to the flows. But the legally challenging deal being considered by the two sides has been lambasted by human rights activists and met with resistance from several EU capitals.

The EU won some backing on Thursday, however, from Europe's leading human rights watchdog.

The Strasbourg-based Council of Europe welcomed the fact that, as part of the migrant-swapping deal, the EU intends to fully process asylum requests for those arriving on Greek islands before deciding whether to send them back to Turkey.

"It is extremely important that every application for asylum should be treated individually and there should be no question of 'blanket' returns," its leader, Thorbjorn Jagland, said. "I hope that these principles will prevail during the negotiations starting today."

But others remain sceptical. The German refugee aid organization Pro Asyl said it is a "farce" to expect Greece to adequately process applications when it has a "de facto non-existent asylum system."

"These fig-leaf procedures won't hide Europe's guilty conscience if large-scale returns of refugees start happening now," added John Dalhuisen of the Amnesty International human rights group, which was staging a protest Thursday outside the leaders' summit venue.

Thousands of people also took to the streets of Spain on Wednesday evening, calling the planned deal a "disgrace." All the political parties in the Spanish parliament have agreed on the need to reject the pact with Turkey.

"The refugees are fleeing from terror and war and cannot here come upon a wall of indifference, a wall of European denial," Socialist leader Pedro Sanchez said this week.

Cyprus is considered to be another potential stumbling block. The island, which is in the midst of delicate reunification talks with its Turkish-backed north, has been resisting Ankara's demands for quick progress on its long-running EU membership bid.

Tusk, who visited Nicosia and Ankara this week as part of his efforts to find consensus, said Thursday that he was "cautiously optimistic - but frankly speaking more cautious than optimistic" of finalizing the plan with Turkey this week.

"We are in talks with Cyprus, with Turkey, with Greece to work out an amicable solution," European Commission President Jean-Claude Juncker added later in the day.

In an interview with Germany's Handelsblatt newspaper, Juncker said that Turkey is not ready for EU membership and "I believe it still won't be ready in 10 years."

The 28 EU leaders will meet with Turkish Prime Minister Ahmet Davutoglu on Friday, after discussing the migration deal amongst themselves on Thursday evening.

Tusk stressed three key principles, noting that the plan must be "acceptable to all 28 member states, no matter big or small;" must "fully comply with EU and international law," and must "effectively help to solve the migration crisis."

"We are moving into difficult talks," he said. "Only if we all work together in a coordinated measure and keep our cool will we achieve success."

Latest news

Syrian opposition rules out future role for President al-Assad

The Syrian opposition said Friday it would not accept any role for President Bashar al-Assad in the future of the war-torn country, reacting to a recent US shift saying that removing al-Assad is no longer a priority for Washington.

Russian Army integrates breakaway forces of Georgian province

Parts of the small fighting forces of the Georgian breakaway province of South Ossetia have been placed under Russian military control, Russian Defence Minister Sergei Shoigu said on Friday.

Czech Republic's Pilsner Urquell beer is now Japanese

Japanese brewing company Asahi completed its takeover of the Czech brewery Pilsner Urquell on Friday, Asahi said in a statement.

Judge approves 25-million-dollar settlement of Trump University case

A US district judge on Friday approved a 25-million-dollar settlement of lawsuits and state fraud allegations against Trump University, the US president's now-defunct business venture.

Former Thai premier Thaksin to junta on reconciliation: 'Cut me out'

Former Thai prime minister Thaksin Shinawatra on Friday announced that he is not interested in the junta-led reconciliation process, three days after the junta handed him a half-a-billion-dollar tax bill for his past business deal.

Dalic: We welcome possible deal between Agrokor and banks

The government welcomes the possibility of an agreement being concluded between the Agrokor food company and creditor banks, and the bill on vitally important companies is not a fallback plan but the result of the government's care for the overall economic and financial stability of Croatia, Deputy Prime Minister and Minister of Economy Martina Dalic told a press conference in Zagreb on Friday.

Croatia, China sign action plan for cooperation in agriculture

The Croatian and Chinese ministries of agriculture on Friday signed an action plan for cooperation in the field of agriculture for the period 2017-2018, the Croatian ministry said in a statement.

ZSE indices up, Agrokor shares in focus of investor interest

The Zagreb Stock Exchange (ZSE) indices on Friday rose by more than 1.8%, with stocks of the Agrokor food and retail concern being in the focus of investor interest again.

Berlin police defend handling of Berlin market attacker

Berlin police defended themselves on Friday against accusations that they stopped surveillance on Berlin Christmas market attacker despite knowing in June 2016 he was dangerous.

Croatia, creditors tailor emergency measures to save tottering giant

Croatia's tottering retail and food giant Agrokor reached an agreement with its creditors, putting its debts standby and allowing it to continue working during emergency restructuring, the Croatian branch of Austria's Erste Bank said Friday.

Agrokor's creditors say standstill agreement to go into force today

A standstill agreement regarding the Agrokor concern's existing financial obligations to banks will take effect on Friday, additional capital will be injected into the concern in the coming days and the concern will be actively restructured, which includes a change of its management, it was said on Friday after a meeting between Agrokor's suppliers and creditor banks.

Palestinians, UN slam Israel's new settlement plan

Palestinians, Israeli activists and the UN lambasted the government of Israeli Prime Minister Benjamin Netanyahu on Friday, a day after it gave the go-ahead for the first new West Bank settlement in a quarter of a century.

South Sudan rebels release three abducted foreign oil workers

South Sudanese rebels have released three foreign engineers they abducted in early March in the oil-rich Upper Nile region, Foreign Affairs Ministry official Mawein Makol Arik said on Friday.

Turkish opposition: Imprisoned party chief has gone on hunger strike

The head of Turkey's pro-Kurdish opposition party has launched a hunger strike from prison.

European leagues threaten Champions League schedule clashes

The European Professional Football Leagues (EPFL) on Friday threatened schedule clashes on Champions League matchdays in an ongoing dispute with the governing body UEFA.

Danish court revokes citizenship of IS volunteer

A Danish appellate court on Friday stripped a man of his Danish citizenship for volunteering to fight for the extremist Islamic State in Syria.

Banks and Agrokor agree on key elements of standstill agreement

Member banks of the coordinating committee of financial creditors and representatives of the Agrokor food company have in principle agreed on key elements of a standstill agreement, which is expected to be signed later today, announcing changes in the company's management team, Erste Bank said in a statement on Friday afternoon.

Syrian man on trial in Sweden; mosque attack labelled terrorism

A Syrian man went on trial Friday in the southern Swedish city of Malmo, charged with terrorism and arson after an attack last year on a building used as an assembly hall by Shiite Muslims.