A unilateral decision by the interior minister to reverse course on a central plank of Germany's asylum policy has forced Chancellor Angela Merkel to edge away from her open-door welcome to refugees and raised questions about her leadership.

Critics say her accommodating message in August that "we can do this" - responding to wrenching scenes of refugees faced with border closures and popular hostility in trying to enter some EU states - have spurred migrants to pour into Germany in ever larger numbers, overwhelming the resources of local authorities.

Tensions within Merkel's conservative bloc worsened this week after it emerged that Interior Minister Thomas de Maiziere tried to tighten controls three weeks ago without informing Merkel or her chief of staff, Peter Altmaier, whom she charged with overseeing the government's handling of the refugee crisis.

At issue is de Maiziere's decision to reapply, from Oct. 21, European rules obliging migrants to request asylum in the first EU country they arrive in, overturning a government decision in August to waive the so-called "Dublin rules" for Syrians.

Germany has taken in the great majority of migrants in a record-breaking flood into Europe of migrants escaping wars and deprivation in the Middle East, Africa and Asia that is likely to exceed 1 million people by year-end.

The initially enthusiastic reception given migrants reaching Germany, Europe's largest and strongest economy, has cooled as local authorities increasingly struggle to house the newcomers.

Technically, de Maiziere was not obliged to flag the closing door to his superiors as it fell under his operational remit. But, by acting unilaterally, he has fed discord within the broad governing coalition of conservatives and Social Democrats (SPD), and undermined Merkel.

"De Maiziere dupes Merkel," ran a headline in Thursday's edition of the daily Sueddeutsche Zeitung.

Compounding Merkel's woes, Finance Minister Wolfgang Schaeuble, a veteran political heavyweight with cult status in the conservative wing of her Christian Democrats (CDU), has backed de Maiziere on the need for steps to stem the refugee flow. Both men have their own reasons for asserting themselves.

Merkel's appointment of Altmaier to oversee management of the refugee crisis effectively demoted de Maiziere, a long-time ally who once held Altmaier's chief-of-staff role.

"Schaeuble is using the opportunity to convey to Merkel that he is not her poodle," said Gero Neugebauer, a political scientist at Berlin's Free University.

He noted that Merkel had not supported Schaeuble's proposal this summer for Greece to temporarily exit the euro because of its huge debt problem.

"Merkel's ability to impose herself has weakened, she has clearly lost authority. Merkel has her back to the wall."

BACKSEAT DRIVING

In an effort to heal the divisions, Merkel backed de Maiziere on Monday after he said Germany would in the future grant some Syrian refugees limited asylum without the right to family reunions, apparently bucking the government line on another strand of refugee policy.

The effort to make nice lasted barely 24 hours when news of de Maiziere's unilateral U-turn on the Dublin rules emerged on Tuesday. Late on Wednesday, Schaeuble stirred the pot further.

Describing Germany's refugee crisis as being like a avalanche, he said: "Avalanches can be caused if a careless skier ... sets some snow on the move."

It was unclear whether the reference was aimed at Merkel, but the comment invited that comparison and prompted a rebuff from Justice Minister Heiko Mass, a Social Democrat, who told Spiegel Online: "People in distress are not a natural disaster."

Coalition sources dismissed speculation of a "putsch" against Merkel, in office for 10 years, as exaggerated. One government official said that if Merkel felt one of her team was impeding her policy she would have sacked them long ago.

But by staking out tough positions, de Maiziere and Schaeuble are backseat-driving Merkel's refugee policy, steering her away from her "We can do this!" catchphrase.

Instead, she is pushing for joint solutions with other EU countries to better share the migrant burden.

"It is now up to Merkel to cut the Gordian knot and give a clear signal internally and externally that Germany cannot take in refugees without limits, and that she is still the mistress of the house," said Neugebauer.