Donald Trump erupted in fury Thursday after Dmitry Medvedev, Vladimir Putin’s attack dog and the deputy chair of Russia’s security council, delivered a stinging humiliation by invoking the MAGA leader’s own derogatory nickname for Joe Biden.

The explosive exchange began when Medvedev mockingly dismissed an ultimatum from Trump demanding Russia reach a Ukraine ceasefire within 10 days or face “debilitating secondary tariffs” on trading partners.

“Trump’s playing the ultimatum game with Russia: 50 days or 10,” Medvedev taunted on social media. “He should remember 2 things: 1. Russia isn’t Israel or even Iran. 2. Each new ultimatum is a threat and a step towards war. Not between Russia and Ukraine, but with his own country. Don’t go down the Sleepy Joe road!”

The “Sleepy Joe” jab clearly struck a nerve. Trump fired back early Thursday on Truth Social.

“Russia and the USA do almost no business together. Let’s keep it that way, and tell Medvedev, the failed former President of Russia, who thinks he’s still President, to watch his words. He’s entering very dangerous territory!” Trump raged.

The “failed president” insult targets Medvedev’s controversial 2008-2012 stint as Russia’s placeholder leader while Putin was constitutionally barred from consecutive terms.

Medvedev had earlier mocked Trump’s theatrical posturing: “Trump issued a theatrical ultimatum to the Kremlin. The world shuddered, expecting the consequences. Belligerent Europe was disappointed. Russia didn’t care.”

The war of words escalated after Trump revised his initial 50-day deadline to just 10-12 days, prompting Medvedev’s devastating comparison to Biden—hitting Trump precisely where it hurts most.