BERLIN: Chancellor Angela Merkel put up a spirited defence of her leadership on Friday, vowing to "fight for my vision" of how to deal with the refugee crisis that has stretched Germany's resources and damaged her standing.

Infighting in Merkel's ruling coalition and a unilateral decision by her interior minister on asylum policy have raised questions about the chancellor's leadership, though coalition sources have dismissed speculation of a "putsch" against her.

A poll for television station ZDF on Friday showed a narrow majority of Germans believed Merkel was doing a bad job of handling the refugee crisis.

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.

The 61-year-old chancellor struck a defiant tone when interviewed for a ZDF programme headlined 'What now Frau Merkel?'

"The chancellor has the situation under control ... I have my vision and I will fight for it," she said, adding that she wanted to address the root causes of the refugees' flight and to better protect the European Union's outer borders.

Asked if she was ready to risk her office over her policy on the refugee crisis, Merkel replied: "No, I have so much to do at the moment," adding a slight laugh. "I am available for voters for this legislative period."

Merkel will complete 10 years in office later this month.

Subject to rapid-fire questions by two interviewers over half an hour, Merkel insisted: "I am not the first chancellor who had to fight for something."

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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.

Local authorities are struggling to cope with the influx and the 'welcome culture' that Germany projected over the summer has soured as concerns mount about how to manage the new arrivals.

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.

Finance Minister Wolfgang Schaeuble, a veteran political heavyweight in Merkel's Christian Democrats (CDU), ratcheted up the strain further on Wednesday by calling the refugee influx an avalanche and suggesting it was started by "a careless skier".

Asked whether she could face questions about her party's trust in her at a CDU conference next month, Merkel responded matter-of-factly: "This is not about a question of trust."

"This is about me fighting, fighting for the plan I have to tackle the causes of the refugee flight," she told ZDF.

Merkel batted away a question about Schaeuble's avalanche comments, praising him as being "a class of his own."

She insisted Germany must send home those migrants who have no right to stay. Berlin is turning away migrants from other European countries but has been welcoming of Syrian refugees.

In August, Germany decided to waive for Syrian refugees the European Union's Dublin rules, which oblige migrants to request asylum in the first EU country they arrive in. It has since toned down that welcome.

Merkel said it was a pleasure to tackle what she described as Germany's biggest challenge since reunification in 1990, and vowed to press ahead with her plans to beef up the EU's outer borders and to tackle the roots of the refugee crisis.

"I think we can do this," she said, sticking to the catchphrase she has deployed throughout the crisis.