STORY: Moscow abandoned its main bastion in northeastern Ukraine on Saturday, in a sudden collapse of one of the war's principal front lines after Ukrainian forces made a rapid advance.
Speaking at a panel discussion at the 'YES' conference Zelenskiy warned that the coming winter will be hard both for Ukraine and Europe.
"When will we have victory? The answer to this question could be given by the stage that is right in front of us. I'm telling you openly: This stage will be difficult. We have to survive this winter."
Ukrainian forces have advanced north from Kharkiv to within 30 miles of the border with Russia and are also pressing to the south and east in the same region, Ukrainian chief commander General Valeriy Zaluzhnyi said on Sunday.
Zelenskiy also shared images said to show his nation's flag being raised over the retaken settlement of Chkalovske.
Reuters was not immediately able to verify Ukraine's battlefield accounts.