Ukrainian President Volodymyr Zelensky on Thursday said Ukraine must be in a position of strength before any peace talks with Russia, as he explained his "victory plan" to EU leaders and NATO defence chiefs in Brussels.

More than two and a half years into the war, Kiev is slowly but steadily losing new territory in its eastern Donbas region and under mounting pressure to forge an exit strategy -- which it says must start with ramped-up Western support.

"Ukraine is ready for real diplomacy, but for it, we must be strong," Zelensky said as he headed into talks with the EU's 27 leaders.

"A forcefully imposed truce instead of fair peace never provided security."

"Russia will resort to diplomacy only when it sees that it cannot achieve anything by force," Zelensky added.

"This is the plan. This is exactly what's needed, and we must create the right conditions to end this war."

After the EU summit Zelensky was to join defence ministers for the first of two days of talks between NATO's 32 member states.

While calling it a "strong signal," NATO secretary-general Mark Rutte cautioned ahead of time he was not endorsing Zelensky's "whole plan" -- which calls first and foremost for an immediate invitation to join the alliance, a plea widely seen as unrealistic.

Zelensky's plan also rejects any territorial concessions, calls for Western allies to lift restrictions on using donated long-range weapons to target Russian military sites, and suggests deploying a "non-nuclear strategic deterrence package" on Ukrainian territory.

The Ukrainian leader has travelled in recent weeks to Washington, Paris, Berlin, Rome and London to defend his plan -- unveiled to Ukrainian lawmakers Wednesday -- but it has yet to earn backing from Western capitals. (AFP)