Former Russian President Dmitry Medvedev said in a post on X on Monday that President Donald Trump was playing "the ultimatum game" with Russia, and that such an approach could lead to a war involving the United States.

Medvedev wrote: "Each new ultimatum is a threat and a step towards war. Not between Russia and Ukraine, but with his [Trump's] own country."

Trump said on Monday that he was disappointed in Russian President Vladimir Putin's failure to end the war in Ukraine, and that he was reducing a deadline to agree to a peace settlement from 50 days to 10 or 12.