Russia, the US and Ukraine agree that a deal on ending almost four years of full-scale war is edging closer but, in the words of President Donald Trump, "one or two very thorny, very tough issues" remain.
Two of the trickiest issues in Washington's 20-point plan involve territory and the fate of Europe's biggest nuclear plant, which is currently occupied by Russia.
The Kremlin agrees with Trump that negotiations are "at a final stage", and Zelensky's next step is to meet European leaders in France on 6 January, but any one of the sticking points could jeopardise a deal.
Vladimir Putin has not budged from his maximalist demand for the whole of Ukraine's industrial Donbas, although Ukraine's Volodymyr Zelensky has offered a compromise.
Russian forces occupy most of the Luhansk region in the east but little more than 75% of Donetsk, and Putin wants it all, including the remaining "fortress belt" cities of Sloviansk and Kramatorsk.
