President Donald Trump’s new deadline for Russia to end the conflict with Ukraine is an additional "step towards war," according to former Russian President Dmitry Medvedev. Medvedev, now the deputy chairman of the Security Council of Russia, cautioned that Trump’s announcement Monday that Russia must end the conflict with Ukraine in 10 to 12 days would not end well for the U.S. "Trump's playing the ultimatum game with Russia: 50 days or 10… 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," Medvedev said in a post on X on Monday. "Don't go down the Sleepy Joe road!"TRUMP MEETS WITH UK PRIME MINISTER STARMER ON HEELS OF EU TRADE DEALWhile Trump announced on July 14 that he would sign off on "severe tariffs" against Russia if Moscow failed to agree to a peace deal within 50 days, Trump said Monday that waiting that period of time was futile amid stalled negotiations. "I’m going to make a new deadline, of about 10 — 10 or 12 days from today," Trump told reporters from Scotland. "There’s no reason for waiting. It was 50 days. I wanted to be generous, but we just don’t see any progress being made."Trump’s remarks come as his frustration with Putin has grown in recent weeks amid no progress toward peace between Russia and Ukraine, and just a day after Russia launched more than 300 drones, four cruise missiles and three ballistic missiles into Ukraine, according to the Ukrainian air force.TRUMP ‘DISAPPOINTED’ IN PUTIN, SAYS HE'LL REDUCE 50-DAY DEADLINE Trump called out Putin for providing lip service during their discussions while not taking proactive steps to end the war. As a result, Trump said he’s grown "disappointed" in the Russian leader and that he’s "not so interested in talking anymore" with Putin. "He talks — we have such nice conversations, such respectful and nice conversation. And then, people die the following night," Trump said Monday. Following Trump’s announcement about whittling down the deadline for a peace deal, Ukrainian President Volodymyr Zelenskyy thanked Trump for his "clear stance and expressed determination" to resolve the conflict."I thank President Trump for his focus on saving lives and stopping this horrible war," Zelenskyy said in a post on X on Monday. "Ukraine remains committed to peace and will work tirelessly with the U.S. to make both our countries safer, stronger, and more prosperous."ZELENSKYY POINTEDLY THANKS TRUMP, AMERICA FOR UKRAINE SUPPORT MONTHS AFTER VANCE'S JAB ABOUT LACK OF GRATITUDE Zelenskyy previously came under scrutiny from Vice President JD Vance in February during an Oval Office meeting for not voicing more gratitude for U.S. support for Kyiv as it battles Moscow.Although Trump has historically boasted about having a solid relationship with Putin, he has publicly voiced increased frustration with Putin in recent weeks as the war rages on between Russia and Ukraine. "We get a lot of bulls--- thrown at us by Putin, if you want to know the truth," Trump said during a Cabinet meeting on July 8. "He’s very nice to us all the time, but it turns out to be meaningless."Fox News Digital’s Caitlin McFall contributed to this report.