MAINZ, Germany — Not even 100 days after she negotiated her way to a fourth term as German leader, Angela Merkel is mired in a political crisis that underscores Europe’s divisions over immigration amid a surge in populism.

The German chancellor faces a showdown with her own interior minister that threatens not only her fragile ruling alliance but also her European Union-wide vision of cooperation to deal with the migrant crisis.

The world's most powerful woman will embark on a weekend of talks ahead of a Monday meeting that could decide her future — and potentially signal the end of the Merkel era. She has been in power since 2005.

Along with French President Emmanuel Macron, Merkel is seen as one of the last bastions of European liberal democracy amid the rise of populism across the continent.

Merkel may be forced to make a U-turn on her open-door policy which has already been scaled back since Germany opened its borders to welcome around 1 million asylum-seekers in 2015. At times more than 10,000 people were arriving daily in the country, which had a population of around 81 million.

Migrants walk from the main station in Dortmund, Germany, in September 2015. Martin Meissner / AP file

Her refugee policy is widely blamed for a surge in support for the far-right Alternative for Germany (AfD), which became the main opposition party after last September's inconclusive election.

Gemany's political turmoil comes amid a rise in populism and anti-immigration sentiment across Europe, including in neighbors such as Poland, Austria and Hungary.

Austrian Chancellor Sebastian Kurz, a conservative critic of Merkel's migration policy, this week pushed for an "axis of the willing" among Austria, Germany and Italy to fight illegal migration.

It is a view shared by German Interior Minister Horst Seehofer, who wants to reject migrants at his country’s border if they have already registered in other E.U. states to the south.

In March, Seehofer told a newspaper that "Islam does not belong to Germany." Seehofer is a member of Merkel's CSU Bavarian allies, who are further to the right than her own Christian Democrats (CDU). He has also vowed to implement a "master plan for quicker deportations."

Chancellor Angela Merkel's coalition is at risk after clashes with Interior Minister Horst Seehofer over Germany's refugee policy. Carsten Koall / Getty Images

Keen not to antagonize Germany’s neighbors, Merkel prefers an E.U.-wide solution and wants to wait until the outcome of a summit of the bloc's leaders on June 28. She has warned that Seehofer's plan could shift the migrant burden onto countries such as Greece and Italy, where she is already unpopular for her economic policies.

"I personally think illegal migration is one of the big challenges for the European Union, so I don't believe we should act unilaterally," she said Thursday. "We should not act in an uncoordinated way, and we should not act at the expense of third parties.”

However, lawmakers from the CSU have backed Seehofer, who said he might defy Merkel by going ahead with his plan next week without her agreement.

If defied, Markel could be forced to fire Seehofer, or lead her CDU to split up the parliamentary bloc in which they have cooperated with the CSU since 1949. That would leave her coalition without a majority and could result in another election.

“Merkel is caught between a rock and a hard place,” said Thomas Walde, co-host of the political affairs show “Berlin Direkt” at NBC’s German partner channel ZDF. “She could either revoke her own policy, which would in effect mean that she is correcting herself and that everything she did so far was wrong. She cannot possibly do that because then she would be a lame duck in her position."

He added: “Or, she could fire the minister of the interior on Monday, if he were to act. But then her coalition partner would leave the coalition, which would leave her without a majority in Parliament, which would be tough. She could try to go for a little while, but in effect that might lead to new elections.”