Ukrainian President Volodymyr Zelensky says that allowing Russia to compete at the 2024 Olympics in Paris would amount to showing that "terror is somehow acceptable".
He said he had raised the issue with French President Emmanuel Macron.
Moscow must not be allowed to use the Olympics for propaganda, he added.
The International Olympic Committee (IOC) has said Russian and Belarusian athletes could compete as neutrals at the Olympics.
But Ukraine has threatened to boycott Paris 2024 if Russian and Belarusian athletes are allowed to compete.
Attempts by the IOC "to bring Russian athletes back into the Olympic Games are attempts to tell the whole world that terror is somehow acceptable", Mr Zelensky said in his nightly video address.
Russia must not be allowed to use the Games "or any other sport event as propaganda for its aggression or its state chauvinism", he added.
The IOC said this week that Russian and Belarusian athletes could compete as "neutral athletes", stating that "no athlete should be prevented from competing just because of their passport".
But Mr Zelensky says there can be no neutrality in sport while his country's athletes are dying on the battlefield.
He also drew comparison with the 1936 Olympic Games in Berlin when the Nazis were in power.
"There was a major Olympic mistake," he said. "The Olympic movement and terrorist states definitely should not cross paths."
The UK government has also condemned the plan to allow athletes to compete neutrally as a "world away from the reality of war".
Mr Zelensky's comments came as Russian forces continued to bombard the Ukrainian region of Kherson into the night, after a day of attacks which left at least three people dead.
Six others were wounded, two of them when a hospital was hit, local officials say.
The Kherson regional administration said the region was shelled almost 40 times on Saturday and was pounded continually on Sunday.
Kherson was the only regional capital to have fallen to Russian forces since the February 2022 invasion, but they were forced into a humiliating retreat in November.
President Zelensky said Russia had also stepped up its attacks in the eastern Donetsk region. He said his forces needed new weapons to confront a "very tough" situation of constant attacks.
"Russia wants the war to drag on and exhaust our forces. So we have to make time our weapon. We have to speed up events, speed up supplies and open up new weapons options for Ukraine," he said.