Russian President Vladimir Putin is stalling at the peace table while preparing a new military offensive in Ukraine, two senior U.S. senators warned Sunday, arguing that the next two weeks could shape the future of a war that has already smashed cities,

A bipartisan pair of US senators met with Ukrainian President Volodymyr Zelensky in Kyiv on Friday and urged stronger sanctions against Russia, while uncertainty swirls over whether the next round of peace talks will move ahead in the coming days.

President Volodymyr Zelenskyy again appealed to the U.S. to apply more pressure on Russian President Vladimir Putin in pursuit of peace talks to end Moscow's war.

A Ukraine presidential adviser says Ukraine is ready to resume direct peace talks with Russia in Istanbul on Monday but insists that the Kremlin provide a promised memorandum setting out its position on ending the war.

The proposed roadmap begins with a full ceasefire of at least 30 days, to be followed by the return of all prisoners held by each side, and of Ukrainian children taken into Russian-held territory, and then a meeting between Ukrainian President Volodymyr Zelenskiy and Russian leader Vladimir Putin.

Ukraine’s foreign minister on Friday accused Russia of stalling peace negotiations, saying that Moscow had yet to share a promised memorandum outlining its peace terms. He said Kyiv wanted to see that document before sending a delegation to a new round of talks Moscow had proposed for Monday in Istanbul.