BRUSSELS >> With another migrant rescue ship stranded in the Mediterranean and both Italy and Malta again refusing to let it dock, European Union leaders will try to find common ground for tackling a growing political crisis that is threatening to undermine the entire EU.

The leaders of about 16 countries — more than half the 28-nation bloc — will take part in what is being billed as “informal talks” in Brussels on Sunday ahead of a full EU summit next Thursday and Friday, where migration will top the agenda.

German Chancellor Angela Merkel said the meeting involves “talking with particularly affected nations about all problems connected with migration.” She said the hope is to see if “we can reach bi-, tri- or even multinational agreements to better solve certain problems.”

The arrival of more than one million people in 2015, most fleeing wars in Syria and Iraq, exposed glaring deficiencies in EU migrant reception capacities and asylum laws. It has fueled tensions among EU nations and anti-migrant parties have won votes in Europe by fomenting public fears of foreigners.

“These rescue ships can forget about reaching Italy,” Italy’s new firebrand interior minister, Matteo Salvini, said today as he assured his anti-migrant base that he would “crush” the human trafficking business.

At the heart of the problem lie deep divisions over who should take responsibility for arriving migrants — often Mediterranean countries like Italy, Greece and increasingly Spain — how long they should be required to accommodate them, and what should be done to help those EU countries hardest hit.

The problem was crystalized last week in a row between Italy’s new populist government, Malta and France over who should take responsibility for 630 people rescued from the Mediterranean Sea off the coast of Libya, the main departure point for people trying to reach Europe.

Amid the mud-slinging, Spain’s new Socialist government agreed to take charge of the migrants and the ship eventually made a weeklong voyage to Valencia.

Today, Spain also announced it had rescued 569 more migrants at sea, many from boats in the Strait of Gibraltar, a busy shipping lane with treacherous currents.

But another rescue ship, the Lifeline of the German NGO Mission Lifeline, was stranded in the Mediterranean off Malta after both Italy and Malta refused to let it dock with its 234 migrants. Lifeline said a merchant vessel, the Alexander Maersk, had another 113 migrants and was also waiting for a port to receive them.

Salvini has demanded that Malta, the EU’s smallest country, allow the Lifeline to dock because it was in the island’s waters.

Maltese authorities today provided humanitarian assistance to the Lifeline’s passengers but Maltese Premier Joseph Muscat stood firm and insisted that Malta had “no responsibility” for the rescue.

The Lifeline “should move from its position toward their original destination to prevent escalation” of the situation, Muscat tweeted.

The rhetoric ahead of the Sunday summit extended north, with Austrian Chancellor Sebastian Kurz saying his country would reintroduce controls on its border with Italy if neighboring Germany were to turn back migrants at its border to Austria.

Like everything to do with migrants in Europe lately, even this meeting is proving controversial. What started as talks between half a dozen leaders now involves at least 16, as others demanded to take part. Four countries in Eastern Europe — the Czech Republic, Hungary, Poland and Slovakia — have refused to attend and reject taking in migrants in general.

Referring to hasty arrangements and a domestic crisis over migration policies within Germany’s coalition government, the fervently anti-migrant Hungarian prime minister, Viktor Orban, said: “We understand that countries have domestic political difficulties, but this can’t result in pan-European confusion.”

“This is an open invitation. Nobody is excluded, everybody is invited. Nobody is forced to attend either,” said Alexander Winterstein, spokesman for the European Commission, where the talks will take place.

With plans to reform Europe’s asylum laws bogged down, EU leaders hope to stop migrants leaving North Africa by paying countries like Algeria, Egypt, Libya, Morocco and Tunisia to hold people until their eligibility for asylum can be established.

French President Emmanuel Macron today proposed that migrants arriving in Europe be placed in “closed centers on European soil” so authorities can quickly decide whether they are eligible to apply for asylum and send home those who don’t qualify.

Speaking in Paris after meeting with new Spanish Prime Minister Pedro Sanchez, Macron said European countries would take in migrants who qualify to apply for asylum, helping to remove the burden of caring for them from Mediterranean nations on the front line like Italy or Spain.

Italy has proposed these asylum-processing “hotspots” be located in the migrants’ countries of origin or transit.

Ironically, the tough talk comes as the number of migrants entering Europe is dropping significantly. The U.N.’s refugee agency says around 80,000 people are expected to arrive by sea this year, about half the number from 2017.

“We do not have a crisis of numbers. We continue to have a crisis of political will,” said UNHCR Europe chief Sophie Magennis.