Russian President Vladimir Putin must give up his "imperial ambitions" that risk destroying Ukraine and Russia and admit he cannot win the war, German Chancellor Olaf Scholz has said.

"That is why we will not accept any peace dictated by Russia, and that is why Ukraine must be able to defend against a Russian attack," Scholz said in his first address to the United Nations General Assembly.

The return of imperialism, with Putin's war against Ukraine, was not only a disaster for Europe, but also for the rules-based global peace order, the chancellor said.

- We support Ukraine with all our forces: financial, economic, charitable and also with weapons, he stressed.

Just before the chancellor left Germany for New York, the government in Berlin promised additional deliveries of weapons from the Bundeswehr's stockpile, including four more self-propelled howitzers.

The German chancellor said that Russia's actions in Ukraine are not only a disaster for Europe, but also for global order and world peace.

"That's why it was so important that 141 countries unequivocally condemned the Russian invasion here in this room," Scholz said, referring to the UN vote in March after Russia attacked its neighbor.