A US proposal to end the war with Russia has been widely leaked and interpreted as favouring Moscow's peace terms.

Russia's President Vladimir Putin has backed the US plan for ending the Ukraine war, saying it can form the "basis of a final peace settlement."

In an address to the nation, President Volodymyr Zelensky said Ukraine faced one of the most difficult moments in its history and faced either the loss of dignity, or the risk of losing the United States as a key partner.