(Reuters) -- German Chancellor Angela Merkel voiced support for Bundesbank chief Jens Weidmann on Sunday, saying she welcomed his warnings about the handling of the euro zone debt crisis and saw his influence within the European Central Bank as positive.

In an interview with public broadcaster ARD, Merkel also cautioned politicians in her coalition against talking up the possibility of a Greek exit from the euro zone, urging them to weigh their words "very carefully."

Weidmann, a former adviser to Merkel, reiterated his opposition to ECB President Mario Draghi's plans to buy the bonds of stricken euro members Italy and Spain in a weekend interview with German magazine Der Spiegel.

Contrary to Weidmann, Merkel said she was confident that the ECB was acting within its mandate for price stability, but she said it was good that the Bundesbank chief was speaking up.

"I think it is good that Jens Weidmann warns the politicians again and again," Merkel said. "I support Jens Weidmann, and believe it is a good thing that he, as the head of the German Bundesbank, has much influence in the ECB."

Merkel allies, particularly the Bavarian Christian Social Union, have stepped up criticism of Greece in recent weeks, with senior CSU lawmaker Alexander Dobrindt saying at the weekend that he expected Athens to be out of the euro zone next year.

Last week, Greek Prime Minister Antonis Samaras visited Merkel in Berlin and issued an impassioned plea for German politicians to tone down their rhetoric, saying it was making it impossible for Greece to win back confidence and launch its privatizations drive.

Merkel said she believed Samaras was making a serious attempt to turn Greece around and issued a similar warning to her fellow politicians in Germany, saying Europe was in a "very decisive phase" in its three-year old crisis.

"My plea is that everyone weigh their words very carefully," she said.

Asked about speculation that the International Monetary Fund might be tempted to pull out of the Greek rescue program, Merkel said she had "no indications" that this was the case.

(Reporting by Noah Barkin, editing by Gareth Jones)