KYIV, Ukraine, May 20, 2025 (BSS/AFP) - Ukrainian President Volodymyr Zelensky on Tuesday accused Russia of not seriously engaging in peace talks and of wanting to continue its three-year invasion, despite a US push for a ceasefire.

US President Donald Trump held calls with both Zelensky and Russian leader Vladimir Putin on the war on Monday, and Russian and Ukrainian officials met in Istanbul on Friday for the first direct talks on the conflict in more than three years.

But the Istanbul talks failed to yield a truce, and Zelensky accused Putin of sending "empty heads" to the negotiating table.

"It is obvious that Russia is trying to buy time in order to continue its war and occupation," Zelensky said in a post on social media.

Trump framed his two-hour conversation with Putin on Monday as a breakthrough, as the Republican seeks an elusive deal to end the war that he had promised on the campaign trail to solve in 24 hours.

But Putin again rebuffed the call for a full, immediate and unconditional ceasefire, instead saying only that he was ready to work with Ukraine on a memorandum outlining a possible roadmap and different positions on ending the war.

Russia invaded Ukraine in February 2022 and has since destroyed swathes of the country's east, killed tens of thousands and now controls around one-fifth of its territory.

Ukraine and Europe are trying to put pressure on Trump to hit Moscow with a new package of massive sanctions after he refused to travel to Turkey for face-to-face talks with Zelensky.

"Ukraine is ready for any negotiation format that delivers results. And if Russia continues to put forward unrealistic conditions and undermine progress, there must be tough consequences," Zelensky said.

Kyiv accused Moscow's negotiators of making unrealistic demands at the Istanbul talks, including sweeping territorial claims that Ukraine has repeatedly rejected.