Addressing the third Ukraine-South East Europe summit in the Croatian city of Dubrovnik, the Ukrainian leader said Kyiv was counting on the support of its important allies including the United States.
"In October, November and December, we have a real chance to move the situation towards peace and long-term stability," he said.
"The situation on the battlefield creates an opportunity to make this choice - a choice in favour of decisive action to end the war no later than 2025."
Zelenskiy did not spell out how and why he perceived such an opportunity.
Russian forces now hold just under 20 per cent of Ukraine, in its east and south.
Moscow's troops continue to steadily gain ground in Ukraine's east while Kyiv's troops control a small chunk of Russian territory across the border, two months after launching an incursion into the Kursk region.
Kyiv has been intensively lobbying allies to allow Western-weapons strikes on military targets deeper inside Russia.
There is great uncertainty for Kyiv ahead of the November 5 US election that could return Donald Trump to the White House.
Trump has said he would seek a quick end to the war, which Kyiv's supporters fear could entail crushing concessions being foisted on Ukraine.
Zelenskiy appealed to the political will of Kyiv's allies to approve his "victory plan", which he said envisages Ukraine's invitation to NATO.
He has pitched the plan as a way to put Ukraine on a strong footing for potential negotiations with Russia, though none are known to be currently planned.
"As I said, the plan is designed to strengthen Ukraine. There can be no scepticism from partners, in my opinion, if they are just not afraid of the Russian Federation. Because we want to get the first step – an invitation" to join NATO, he told reporters after the summit.
Russian Foreign Ministry Spokeswoman Maria Zakharova said on Wednesday that achieving a just peace in Ukraine would be impossible if Kyiv lost its neutrality by joining a bloc such as the US-led NATO military alliance.
Russian President Vladimir Putin has said peace talks can only begin if Kyiv agrees to abandon large swaths of territory claimed by Moscow and drops its bid to join NATO.
Zakharova, speaking about reports that the West was discussing an option in which Ukraine could join NATO in return for accepting Russian control over a swathe of Ukrainian territory, said that achieving a just peace in Ukraine would be impossible without ensuring that Ukraine's status was neutral and non-aligned.
Meanwhile, Pope Francis will meet Zelenskiy on Friday morning, the Vatican said.
Francis last saw the Ukrainian president on the sidelines of the Group of Seven summit in southern Italy in June.
The two also met at the Vatican in December 2023.
Zelenskiy is also expected to hold talks with Italian Prime Minister Giorgia Meloni during his stay in Rome this week.
Francis drew the ire of Ukrainian officials in March when he suggested they should have the courage of the "white flag" to negotiate an end to the war with Russia, following Moscow's full-scale invasion in February 2022.
Zelenskiy dismissed the pope's remarks as "virtual mediation" from a distance.
Francis recently announced he will make Melbourne-based Ukrainian bishop Mykola Bychok one of 21 new Catholic cardinals, during a ceremony to be held December 8.
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