With pressure increasing for eurobonds to share the debt of EU member countries, Merkel laid down the law, turning her repeated “no” to the idea into a “never”.
She was speaking to a meeting of the parliamentary group of her business-friendly coalition partner the Free Democratic Party on Tuesday when she made the uncharacteristically strong statement.
And on Wednesday she addressed the full parliament and told MPs there were "no quick, no easy" solutions, nor a "magic formula", and called for the problem to be tackled at its roots.
"Everything else is doomed to failure from the start. At best it is window dressing," she told the Bundestag lower house of parliament in a speech lasting around 25 minutes punctuated by applause.
Under pressure from financial markets and international partners to come up with convincing responses to the more than two-year long eurozone crisis in Brussels, Merkel said she was under "no illusion".
"There will be controversial discussions in Brussels. And yet again, all eyes, or at least several eyes, will be on Germany."
"But I repeat that Germany's strength is not unlimited. Germany's power is not endless," she warned.
The EU is pushing for a collective financing of members' debt, a bank union and eventually a Treasury office to oversee the currency, the Die Welt newspaper said on Wednesday.
Commission President Jose Manuel Barroso stressed that the plan was not only about European economic integration but also to generate more confidence in the euro and get nations to commit to the European project.
Merkel is said to be looking increasingly isolated in her opposition to the idea.
The latest – fifth – European Union bailout candidate is Cyprus, where sources expect the nation will need as much as €10 billion, or more than twice the country's annual output.
Europe's politicians have engaged in a flurry of shuttle diplomacy to thrash out a solution, culminating in Merkel's dinner with French President Francois Hollande on Wednesday.
The short-term problems could feed into long-term ones, which are being pushed to the back burner as EU officials deal with new immediate emergencies. Big euro countries like Spain and Italy are facing increasing financial difficulties as they have to pay ever higher interest rates to borrow money.
The head of Merkel's Christian Democratic Union party's economic council, Kurt Lauk, insisted that Cyprus not be allowed to take over the EU council presidency, which it is set to do July 1, because of its economic problems.
A country that for years did not do its own economic homework cannot exert such a function, Lauk said. The German foreign ministry immediately rejected that idea.