Munich - Hardliners of Chancellor Angela Merkel's conservative bloc are poised to give the German leader an ultimatum to tighten asylum rules or risk pitching the country into a political crisis, as tensions over migration reignite across the EU.
Three years after her decision to open Germany's borders to migrants fleeing war in Syria and Iraq and misery elsewhere, Merkel is still struggling to find a sustainable response to the complaints from her Bavarian allies CSU over her refugee policy.
June 18 is "destiny day for Angela Merkel. For the government," wrote the mass-circulation newspaper Bild on Sunday.
European Union countries are once again at loggerheads over migration, triggered by Italy's recent refusal to allow a rescue ship carrying 630 migrants to dock.
Malta also turned the vessel away, sparking a major EU row until Spain agreed to take in the migrants.
In Germany, Interior Minister Horst Seehofer of the CSU has been one of the fiercest critics of Merkel's liberal stance, under which a million asylum seekers have been admitted into Germany since 2015.
He now wants to turn away at the border new arrivals who have previously been registered in another EU country -- often their first port of call, Italy or Greece.
But Merkel says that would leave countries at the EU's geographic southern periphery alone to deal with the migrant influx.
Instead, she wants to find a common European solution at the June 28-29 EU summit.
Top brass from Merkel's CDU and Seehofer's CSU party are huddling for separate talks in Berlin and Munich.
Both party leaders are expected to address the media on Monday afternoon.
Ahead of the meetings, CSU secretary general Markus Blume said Seehofer's "masterplan" on migration had the party's "full support".
- Anti-immigrant boost -
Popular misgivings over the massive migrant influx have given populist and anti-immigration forces a boost across several European nations, including Italy and Austria where far-right parties are now sharing power.
In Germany, voters in September's elections handed Merkel her poorest score ever, giving seats for the first time to the far-right anti-Islam AfD.
Several high profile crimes by migrants have also fuelled anger. They include a 2016 Christmas market attack by a failed Tunisian asylum seeker and the recent rape-murder of a teenage girl allegedly by an Iraqi.
With an eye on October's Bavaria state election, the CSU is anxious to assure voters that it has a roadmap to curb the migrant influx.
Seehofer struck a more conciliatory tone when he told Bild on Sunday that "it is not in the CSU's interest to topple the chancellor, to dissolve the CDU-CSU union or to break up the coalition.
"We just want to finally have a sustainable solution to send refugees back to the borders."
He has the nuclear option of seeking approval from his party to shut Germany's borders immediately in defiance of Merkel, or the less aggressive choice of giving her an ultimatum of two weeks to sort out a deal with other EU nations.
Signalling that he is leaning towards the latter option, Seehofer wrote in a column in Frankfurter Allgemeine Zeitung that "it is essential that the EU summit takes a decision at the end of June.
"The situation is serious but still solvable," he wrote.
- 'Almost a miracle' -
An act of rebellion from Seehofer could force Merkel to sack him, which "would be the end of the government and the alliance between CDU and CSU," an unnamed CDU source told Bild.
If Merkel is given a two-week ultimatum, she would still face the challenge of persuading EU governments to sign up to a common plan on the migrants.
Central and eastern EU nations such as Hungary and Poland have either refused outright or resisted taking in refugees under an EU quota system.
A populist-far right government in Italy, as well as the conservative-far right cabinet in neighbouring Austria, have also taken an uncompromising stance on immigration.
Merkel's talks on Monday evening with Italian Prime Minister Giuseppe Conte could prove crucial if she is to have any chance of forging an agreement in Brussels.
On Tuesday, she will huddle with French President Emmanuel Macron.
Berlin is also reportedly preparing to call a meeting between Merkel and the leaders of several EU frontline nations in the migrant crisis ahead of the Brussels summit.
Welt daily said "it would be almost a miracle if she emerges a winner from the next EU summit."
By Ralf Isermann with Hui Min Neo in Berlin