President Volodymyr Zelensky signed a decree on Tuesday formally declaring the prospect of any Ukrainian talks with Kremlin leader Vladimir Putin "impossible," but leaving the door open to talks with Russia.
The decree formalized comments made by Zelensky on Friday after the Russian president proclaimed four occupied regions of Ukraine to be a part of Russia, in what Kyiv and the West said was an illegitimate farce.
"He (Putin) does not know what dignity and honesty are. Therefore, we are ready for a dialog with Russia, but with another president of Russia," Zelensky said on Friday.
Ukrainian forces have broken through Russian defenses in the south of the country and expanded a rapid offensive in the east, seizing back territory in areas annexed by Russia, which invaded Ukraine in February.
Putin, who turns 70 this week, has dominated Russia's political landscape for more than two decades and could run for office two more times under constitutional reforms he presided over, potentially remaining in power until 2036.