BERLIN—Chancellor Angela Merkel roundly rebuffed U.S. President Barack Obama's call for Germans to aid the global recovery by spending more and relying less on exports, even as she warned that Europe's own financial crisis is far from over.

In an interview with The Wall Street Journal in her Berlin chancellery, an unapologetic Ms. Merkel said the nations that share the beleaguered euro have merely bought some time to fix the flaws in their monetary union. She called on the Group of 20 industrial and developing nations meeting in Toronto this weekend to send a signal that tougher financial-market regulation is on its way to dispel the impression that momentum is fading amid resistance by big banks.

She took aim at an idea voiced by France, the U.S. and others that Germany should help global producers by spurring its persistently weak consumer demand and ending its dependence on unsustainable spending elsewhere. The latest call came in a letter last Friday from Mr. Obama to the G-20, in which he asked big exporters—Germany, China and Japan—to rebalance global demand by boosting consumer spending.

Ms. Merkel countered that Germany's growth and employment are rising—and therefore the world's fourth-largest economy has no reason to rethink its dependence on its powerhouse industrial sector and large trade surplus. "German export successes reflect the high competitiveness and innovation strength of our companies," she said. "Artificially reducing Germany's competitiveness would be of no use to anyone."

The U.S. reiterated its stance Wednesday. "It is important for European growth in particular, and the world more generally, that advanced surplus economies in Europe strengthen the contribution of internal demand to growth," a senior administration official said.