WASHINGTON — President Donald Trump is expressing new skepticism about the possibility of a meeting between Ukrainian President Volodymyr Zelenskyy and Russian President Vladimir Putin, as the chances for a summit between the conflicting nations seem to be diminishing.

“I’m not sure if they’ll meet — maybe they will, maybe they won’t,” Trump remarked Monday at the White House during a session in the Oval Office with South Korean leader Lee Jae-myung. “It’s up to them. It takes two to tango. I always say it. They should meet, I believe, before I have a meeting and likely seal the deal, but I think that’s the right approach.”

Trump commended Putin for visiting the United States for discussions, noting that Putin was hesitant to do so, but he admitted that peace negotiations appear to be stalling.

This represents a shift in attitude just over a week after Trump hosted Putin in Alaska for a fast-paced summit intended to resolve the three-year impasse in the Russia-Ukraine conflict. Trump had originally proposed that consecutive meetings between the main parties could take place within days or weeks.

However, he acknowledged Monday that coordinating the meetings has turned out to be more difficult than expected and described the confrontation as “personal” for both leaders, driven by deep-seated hostility.

Highlighting the situation, two Russian cruise missiles struck a U.S. electronics plant in Ukraine last week, indicating that Moscow remains devoted to the conflict despite Washington’s demands for an end to the violence.

Even so, Trump struck an optimistic note, saying he believes “we’re gonna get that war straightened out,” and he also warned that there “could be very big consequences” if Putin and Zelenskyy fail to meet soon.

“We’ll see what happens over the next week or two,” he said, extending the timelines and adding that he would be prepared to “step in very strongly” if progress stalls.

On security guarantees, Trump said earlier in the day that the United States would support European efforts to secure Ukraine but emphasized that Europe would undertake the most “significant” commitments. “They’re right there,” he said. “But we’ll back it up, because I want to stop seeing people being killed.”

Trump’s summit with Putin on Aug. 15 ended abruptly with a planned lunch pulled from the schedule and no ceasefire deal, but Trump signaled progress, calling it “productive.” Zelenskyy and European leaders rushed to the White House for a high-level meeting after the summit with Putin. At the time, the White House touted the urgency of the moment, noting that “every single one of them got on a plane 48 hours later” to join the talks.

During that meeting, Trump stepped out to call Putin and later said on Truth Social that he had begun “the arrangements for a meeting” between Zelenskyy and Putin, after which they would have a trilateral meeting involving Trump himself. Kremlin officials downplayed the idea, with Foreign Minister Sergey Lavrov casting doubt over the future of the peace push in an interview Friday with NBC News’ “Meet the Press.” There was no such meeting on the calendar, Lavrov said, adding that key issues, including territorial disputes and security guarantees for Ukraine, remain unresolved.

By the end of the week, Trump’s frustration appeared to be mounting. “I’m not happy about anything about that war. Nothing. Not happy at all,” he said Friday, warning that “the next two weeks” could be pivotal.

Asked what would happen at the end of those two weeks, Trump said he would weigh “massive sanctions or massive tariffs or both. Or do we do nothing and say it’s your fight.”