THIERRY CHARLIER/AFP/Getty Images Tusk’s summit task: ‘European unity’ The emergency meeting on refugees comes as countries remain deadlocked.

EU leaders will gather for an emergency summit next week and make another attempt to show unity in dealing with Europe’s migration crisis.

The decision by European Council President Donald Tusk to call the summit, set for the evening of September 23 in Brussels, comes after EU countries failed this week in a meeting of interior ministers to agree on a plan to relocate 120,000 refugees across Europe.

It also comes after a phone call on Tuesday from German Chancellor Angela Merkel to Tusk, saying a summit was needed to break the logjam, and to respond to scenes of mayhem along the Hungary-Serbia border as thousands of refugees continued to arrive every day from the Middle East hoping to enter the EU.

“Merkel said that she wants to keep European unity,” said an EU diplomat. “This will be Tusk’s job.”

Several countries remain opposed to the refugee relocation proposal, put forward last week by Commission President Jean-Claude Juncker, because it would impose mandatory quotas for the acceptance of asylum-seekers.

EU leaders still hope that particular issue is resolved before Wednesday’s summit even happens, officials said. Another meeting of the bloc’s interior ministers is set for Tuesday, with the relocation plan as the main order of business.

The summit itself is billed as an “extraordinary, informal” meeting, and the exact agenda is still being developed “in close consultations with other member states and institutions,” said Preben Aamann, Tusk’s spokesman.

At the summit, Aamann added, “Tusk would like to focus on other immediate issues that need tackling urgently if we want to get the situation under control, including in our neighborhood.”

Those issues are likely to include the situation in Turkey and Syria, and how to deal with the political roots of the refugee crisis, according to another EU official.

But in the days leading up to both of next week’s crucial meetings, the issue of relocating asylum-seekers remains at an impasse. Some Eastern European countries are still opposed to the Commission proposal, which would set mandatory quotas for EU member states to accept asylum-seekers now in Italy, Greece and Hungary.

On Thursday a Commission spokeswoman denied reports that the EU executive body was ready to drop the insistence on mandatory quotas. Even though the new relocation scheme will not be officially on the summit agenda, Tusk could be forced to confront it if there is no agreement the day before by interior ministers.

The 'nuclear' option

EU officials have spent days trying to broker an agreement on the new relocation plan, and are hoping to avoid turning to a last-ditch, “nuclear” option: a qualified majority vote that would force through a decision over the objection of countries opposed to it.

But according to one EU diplomat it is "very likely" that a decision-making option normally used for less controversial issues could come into play on this one.

It's known by one of the acronyms frequently heard in Brussels policy-wonk conversations: QMV, for qualified majority voting. It is a principle introduced to avoid the need to find a unanimous consensus on every issue and means that a decision can instead be taken if two conditions are met: when 55 percent of EU member states vote in favor of a measure, and when it is supported by member states representing at least 65 percent of the total EU population.

The prospect of using QMV to impose a plan for the relocation plan first emerged after EU countries failed Monday to reach a consensus on it.

EU Migration Commissioner Dimitris Avramopoulos, at the end of that meeting, stressed that “a majority of the member states are ready to move forward, but not all.”

With that majority, the Council could push forward the new plan using QMV. But doing so on such a contentious issue would be politically risky.

“As far as I can recall it has never been used on delicate issues like migration,” said a senior EU diplomat.

The way forward

By Thursday, little was clear about how the EU will reach a decision on a crisis that shows signs of only getting worse. Leaders were still up in the air about whether a final decision could be made at ministerial level or at the summit.

So far, reluctant countries, mainly in Eastern Europe, have not softened their line. Slovakia, one of the strongest opponents of the relocation plans put forward by the Commission, will resist implementing EU decisions to impose mandatory quotas of asylum seekers on member states, Prime Minister Robert Fico said on Wednesday. He told parliament that Slovakia would not accept any decision made by a qualified majority.

Nobody will dictate to us what to do — Robert Fico

"Nobody will dictate to us what to do," Fico said.

Nuclear fallout

Even if qualified majority voting could offer a way out of the standoff, it would be politically risky and even damaging to European unity for a number of reasons, EU sources say.

First of all, Europe works by consensus, trying to find the larger possible majority on every issue — and with qualify majority some countries get cornered.

Secondly, diplomats worry there would also be implications for the very people they are trying to help: the refugees. "We are talking about human beings. Is it easy to imagine how refugees would be welcomed by the local population in a state that openly opposes their arrival?” said one EU official.

Germany is ready to consider the QMV option if needed, an EU diplomat said, pointing out that Berlin is very much aware of the problematic consequences it could entail.

Among countries opposing this new relocation scheme, mainly in Eastern Europe, there is a mixture of anger and defiance about the possible use of a qualified majority.

It would be “very dangerous” to use it, said a Hungarian diplomat. “Legally, it would be feasible but it would be a political and institutional problem.”

Hungarian Prime Minister Viktor Orbán, in an interview with Die Welt, said a decision from Europe to impose quotas over some countries' objection would not be a wise decision, but “it will be the law and we will have to accept it."

The Slovak interior minister, Robert Kalinak, said his country was not afraid of being outnumbered on the issue. “There is the real possibility of the use of a qualified majority, but just because of this threat we cannot abandon our principles,” he told journalists after Monday's failed ministerial meeting.

Others made clear that they are doing their best to avoid this option.

In a meeting with the EU foreign policy chief Federica Mogherini, Czech Foreign Minister Lubomír Zaorálek stressed the need for a common solution and to avoid the use of qualified majority, said an Eastern European diplomat. A Polish diplomatic source also stressed that steamrolling reluctant countries would be counter-productive.

"Qualified majority vote is not the way forward,” the source said.

Hans von der Burchard contributed to this article.