U.S. President Donald Trump said he plans to speak to Russian President Vladimir Putin on Tuesday and discuss ending the war in Ukraine, after positive talks between U.S. and Russian officials in Moscow.

“We want to see if we can bring that war to an end,” Trump told reporters on Air Force One during a late flight back to the Washington area from Florida. “Maybe we can, maybe we can’t, but I think we have a very good chance.

“I’ll be speaking to President Putin on Tuesday. A lot of work’s been done over the weekend.”

Trump is trying to win Putin’s support for a 30-day ceasefire proposal that Ukraine accepted last week, as both sides continued trading heavy aerial strikes through the weekend and Russia moved closer to ejecting Ukrainian forces from their months-old foothold in the western Russian region of Kursk.

There was no immediate response from the Kremlin to a request for comment from Reuters. The Kremlin said on Friday that Putin had sent Trump a message about his ceasefire plan via U.S. envoy Steve Witkoff, who held talks in Moscow, expressing “cautious optimism” that a deal could be reached to end the three-year conflict. In separate appearances on Sunday TV shows in the United States, Witkoff, Secretary of State Marco Rubio, and Trump’s national security adviser, Mike Waltz, emphasized that there were still challenges to be worked out before Russia agrees to a ceasefire, much less a final peaceful resolution to the war.

Russia demands ‘ironclad’ guarantees

Russia would want “ironclad” guarantees in any peace settlement that NATO nations exclude Kyiv from membership and that Ukraine will stay neutral, according to a Russian deputy foreign minister’s remarks published on Monday. In a wide-ranging interview with Russian media source Izvestia that made no mention of the ceasefire plan, Deputy Foreign Minister Alexander Grushko stated that any long-term peace accord with Ukraine must fit Moscow’s requirements. “We will demand that ironclad security guarantees become part of this agreement,” Grushko told Izvestia. “Part of these guarantees should be the neutral status of Ukraine, the refusal of NATO countries to accept it into the alliance.”

Putin has stated that his military entry into Ukraine was motivated by NATO’s gradual expansion, which posed a threat to Russian security. He has asked that Ukraine abandon its NATO goals, that Russia maintain authority over all occupied Ukrainian territory, and that the Ukrainian army’s size be reduced. He also wants Western sanctions lifted and a presidential election in Ukraine, which Kyiv considers premature while martial law is in effect.