BERLIN--Germany's Chancellor Angela Merkel Thursday defended her tough stance against Russia, stressing that economic sanctions remain "unavoidable" as long as the Kremlin disrespects countries' right to self-determination and European values.

Her comments come as a sharp decline in the ruble has sparked concerns about the economic deterioration in Russia and the security implications of the sanctions that the West imposed against Russia over its policy regarding Ukraine.

The end of the Cold War has enabled countries in eastern Europe to pursue their own paths and this right must be defended, Ms. Merkel told the lower house of the German parliament ahead of a European Union summit.

"If we tolerated that this self-determination could be given up, then this would mean nothing less than a renewed division of Europe in spheres of influence, and division of Europe," Ms. Merkel told lawmakers. "This would be a considerable step back for Ukraine, but it would actually also be a considerable step back for Europe's security and for Europe as a whole. That's why we can't allow this. And we therefore won't allow this."

The EU and the U.S. have been in a standoff with Russia over the Kremlin's policy in Ukraine for most of the year. The West's imposed economic sanctions against Russia, falling oil prices and the slide of the ruble have hurt the Russian economy considerably over the past months.

Berlin has said, however, that there is no direct relation between the sharp fall in the ruble and the sanctions.

Ms. Merkel stressed that she is seeking a dialogue with Russia to achieve a secure European relationship with Russia and is "not against Russia."

"It's up to Russia to take up our offer for dialogue on the basis of European peace, order and values," she said. "As long as we haven't reached this goal...sanctions remain unavoidable. But I want to emphasize once again that they were not and are not end in themselves."

The Ukraine crisis will also be a topic when EU leaders gather in Brussels Thursday evening.

Write to Andrea Thomas at andrea.thomas@wsj.com

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