Ukraine may agree to stop fighting and give up territory already held by Russia, as part of a European-backed peace plan.
Volodymyr Zelensky told European leaders that they should reject any solution proposed by Donald Trump, in which Ukraine gives up further territory but that Russia can be allowed to keep some of the land it has taken.
This means freezing the front line where it is and giving Russia de facto control over the territory it has occupied in Luhansk, Donetsk, Zaporizhzhia, Kherson and Crimea.
The softening of the negotiating position comes ahead of important talks between Donald Trump and Vladimir Putin in Alaska this Friday.
"The plan can only be linked to the current positions held by the military," a Western official said, characterizing a busy diplomatic weekend between Kiev and its allies.
Ukraine and Europe are increasingly worried that Trump and Putin could negotiate an end to the long war for Zelensky's "head".
"I have a lot of fear and a lot of hope," Poland's prime minister said on Monday.
Donald Tusk added that US officials had pledged to consult with European leaders ahead of face-to-face talks on Friday between Trump and Putin in Alaska.
The main concern among Europeans was an alleged peace plan approved by Moscow, which included freezing the front lines in southeastern Ukraine if Kiev agreed to withdraw from the Donetsk and Luhansk areas it controls.
European diplomats say there has been no apparent change in Putin's overall war goals, which seek to topple Ukraine's Western-faced government and replace it with a representative friendly to Moscow.
Russia still aims to "completely capitulate" to Kiev, including blocking any prospect of NATO membership and demilitarization, according to a report published by the Institute for the Study of War, the Washington-based group.