Moscow, Russia - Former Russian president Dmitry Medvedev slammed US President Joe Biden and rejected calls for Russia's troops to withdraw from Ukraine, saying his country would fall apart if it allowed such a move.

Ukraine countered by saying it expects to receive fighter jets from NATO allies in the near future. But the ferocity of Medvedev's comments may alarm the West, especially after Russian President Vladimir Putin announced his country was suspending participation in a key nuclear arms treaty.

"If the US stops supplying weapons to the regime in Kiev, then the war will end," the deputy head of Russia's National Security Council wrote on Wednesday on the Telegram news channel, implying Moscow could then crush Kiev with a new offensive.

"If Russia ends the special military operation without a victory, then Russia will cease to exist, it will be torn to pieces," Medvedev wrote.

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Russia launched the full-scale war against Ukraine last year on February 24.

With typically belligerence, Medvedev also criticized Biden for addressing the Russian people from Warsaw on Tuesday in front of Polish citizens.

"Who is this strange grandpa anyway, speaking with a lost look from Poland? Why is he appealing to the people of another country at a time when he has enough problems in his own?"

Medvedev accused the US, which he said has caused many wars around the world, of "megalomania" and said Biden was senile. He spoke of being on the brink of a "world conflict" and even threatened the use of nuclear weapons.

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Biden delivered a speech in Warsaw on Tuesday to mark the first anniversary of the war. He concluded the speech by directly addressing the people of Russia.

The United States and Europe – who provide weapons and financial assistance to Kiev – do "not seek to destroy or control Russia," Biden said.

"President Putin chose this war," said Biden. "Putin can end the war with one word."