German chancellor Friedrich Merz. AFP
Conservative election winner Merz said the more than three-year-old war "is directed against the entire political order of the European continent".
Merz's CDU/CSU alliance has sealed a coalition deal with the centre-left SPD after winning an election in February. His government is set to take office on May 6.
Speaking at a party meeting in Berlin to sign off on the coalition contract, Merz said Germany was ready to "once again assume leadership responsibility" in the European Union.
He acknowledged there had been little "euphoria" so far greeting the coming change at the top, adding: "This is not the time for euphoria. The pillars we have relied on over the past years and decades are faltering around us".
"Trust in our democracy is damaged like never before in our country's post-war history," he said, adding that "our economy is weakening".
"(Europe) is under threat from outside by an imperialistic, authoritarian war to the east and also from frightened, insecure and even radicalised citizens within its borders," he said.
Support for Ukraine was part of "a struggle for the preservation of peace and freedom in our country", Merz said.
"We are also directly threatened by this war and by Russia," he added, pointing to acts of sabotage and interference blamed on Russia, including what he called a "systematic" disinformation campaign.
"We therefore oppose all these attempts to divide our country and destabilise the countries of Europe and our democracy with determination and, above all, with a readiness to defend ourselves."
Pointing to the return of US President Donald Trump, but without naming him, Merz said that "we have come to realise that we can no longer be sure of the transatlantic relationship in the spirit of freedom and rules-based order".
Germany's election on February 23 took place amid a surge in support for the far-right and Moscow-friendly Alternative for Germany (AfD) party, which finished in second place with more than 20 percent of the vote.
The AfD has since continued to grow in popularity, with several recent surveys showing it as Germany's most popular party.
Merz said his goal remained to once more make the AfD "a marginal phenomenon", including by cracking down on irregular immigration and eliminating the "pull factors that still exist in Germany".
But he warned that unless the government meets the demands of most voters, then Germany could end up in a situation where "we are perhaps at some point no longer able to govern".
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