BERLIN—German Finance Minister Wolfgang Schäuble said his country is prepared to raise pressure on Russia to help stabilize Ukraine, sending a signal on the eve of Ukraine's presidential election that Europe's leading economic power isn't shy about confronting Moscow.

"We want good, partner-like relations," Mr. Schäuble said in an interview. But he warned: "If Russia does not follow the rules, then we won't seek military escalation, but we will of course use our political and diplomatic abilities to increase...