Merkel's comments to Focus news weekly come a month before elections in Europe's biggest economy and days after the woes of debt-mired Greece lurched
onto the campaign trail.
"I am expressly warning against a haircut," she said, according to a pre-released copy of the interview.
"It could trigger a domino effect of uncertainty with the result that the readiness of private investors to invest in the eurozone again fall to nothing," she said.
The term haircut means a reduction in the value of debt bonds owed, with the effect that investors who have loaned money lose part of the eventual repayment of the amount owed.
Merkel said Greece's debt and structural reforms would again be studied in 2014, as planned. "Until then the country still has much to do and must continue consistently to implement its reforms," she added.
She pointed to a second-quarter return to growth in the eurozone and said there were also "positive developments" in Greece.
Finance Minister Wolfgang Schaüble made waves last week, saying at a campaign event that Athens would need another rescue after 2014, seen as marking a shift in Germany's position.
Schaüble insisted however that creditors would not be forced to take more losses on their Greek holdings.
Greek Finance Minister Yannis Stournaras said Sunday that if a third bailout for Greece was necessary in 2014, it would be worth around €10 billion ($13.3 billion) and would not be contingent upon the implementation of new austerity measures.
"If there is need for further support to Greece, it will be in the order of about 10 billion euros, or much smaller than the previous programmes," Stournaras told Greek newspaper Proto Thema.
Two aid programmes from eurozone allies and the International Monetary Fund have given Athens a lifeline since the financial crisis began.
The first, in May 2010, consisted of loans of €110 billion, while the second, passed in February 2012 and in place until July 2014, provided the crisis-stricken country with €140 billion.
Merkel faces elections for a third term on September 22nd and the issue of Greece could prove contentious as German taxpayers feel they have already stumped up the lion's share of European bailouts.
The chancellor already sought to defuse the issue, saying a day after Schaüble's comments that any decision on a new aid package for debt-mired Greece would not come before next year.
Heavily indebted Greece has received two international bailouts in exchange for reforms including major public sector cuts in jobs, pay and pensions.