The United States says it has made significant progress on crafting a plan to end the Russia-Ukraine war during talks with Ukrainian and European officials in Switzerland.

US Secretary of State Marco Rubio on Sunday said “a tremendous amount of progress” was made on a US proposal to end Russia’s nearly four-year war on Ukraine, though he provided scant details.

“We’ve really moved forward, so I feel very optimistic that we’re going to get there in a very reasonable period of time, very soon,” Rubio told reporters at the US mission in Geneva.

Rubio said work remained to be done on questions, including the role of NATO and security guarantees for Ukraine, but that his team had narrowed down unresolved issues in a 28-point peace plan for Ukraine championed by US President Donald Trump.

“And we have achieved that today in a very substantial way,” he said.

Andriy Yermak, head of Ukraine’s delegation, echoed Rubio’s sentiments, telling reporters that they made “very good progress” and were “moving forward to the just and lasting peace Ukrainian people deserve”.

Earlier, Trump said Ukraine had not been grateful for the US efforts to end the war, prompting Ukrainian officials to stress their gratitude to the US president for his support.

“UKRAINE ‘LEADERSHIP’ HAS EXPRESSED ZERO GRATITUDE FOR OUR EFFORTS, AND EUROPE CONTINUES TO BUY OIL FROM RUSSIA,” Trump posted on his social media site on Sunday morning.

Moments later, Ukrainian President Volodymyr Zelenskyy said on X that his country was “grateful to the United States … and personally to President Trump” for the assistance that has been “saving Ukrainian lives”.

Zelenskyy may visit the US in the coming days for direct talks with Trump, the CBS news channel reported, citing US and Ukrainian officials.

Trump had given Ukraine until November 27 to approve his 28-point plan, but Kyiv wants changes to a draft that accepts a range of Russia’s hardline demands, including requiring the invaded country to cede territory, cut its army and pledge never to join NATO.

The peace plan has triggered alarm in Kyiv and European capitals. Zelenskyy has said his country could face a stark choice between standing up for its sovereign rights and preserving the US support it needs.

Asked about whether he believed a deal could be reached by Thursday, as demanded by the US president, Rubio said “the deadline is we want to get this done as soon as possible”.

Rubio called the US proposal a “living, breathing document” that would continue changing. He also said any final product – once it is ready – will still have to be presented to Moscow.

“Obviously, the Russians get a vote here,” he said.