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.

Kyiv said it was committed to the search for peace, but that it was waiting for a memorandum from the Russian side setting out their proposals.

Russia said it’s sending a delegation to Istanbul Monday for a second round of talks with Ukraine amid last-minute wrangling over Kyiv’s insistence that Moscow outline its peace proposals before any meeting.