BERLIN — Emphasizing that “the territorial integrity of Ukraine cannot be called into question,” Chancellor Angela Merkel of Germany appealed forcefully to Russia on Thursday to abandon what she called the politics of the 19th and 20th centuries, and to find a peaceful negotiated solution to a crisis “in the heart of Europe.”

The alternative, she suggested in a 20-minute speech in Parliament, her strongest public statement since the start of the crisis in Ukraine, was huge damage to Russia’s long-term interests.

“Ladies and gentlemen, if Russia continues on its course of the past weeks, it will not only be a catastrophe for Ukraine,” Ms. Merkel said. “We would not only see it, also as neighbors of Russia, as a threat, and it would not only change the European Union’s relationship with Russia,” she said. “No, this would also cause massive damage to Russia, economically and politically.”

Instead of choosing to help Ukraine, Ms. Merkel said, Russia was exerting old-fashioned military pressure.