The letter reflects a renewed push by Kyiv to secure an invitation to join NATO, which is part of a "victory plan" outlined last month by President Volodymyr Zelenskyy to end the war triggered by Russia's 2022 invasion of Ukraine.

Ukraine says it accepts that it cannot join NATO until the war is over but extending an invitation now would show Russian President Vladimir Putin that one of his main goals – preventing Kyiv from becoming a NATO member – could not be achieved.

NATO has declared that Ukraine will join the alliance and that it is on an "irreversible" path to membership. But it has not issued a formal invitation or set out a timeline.

NATO diplomats say there is no consensus among alliance members to invite Ukraine at this stage. Any such decision would require the consent of all NATO's 32 member countries.

But Sybiha argued in his letter, written in English, that this was the right time to issue an invitation.

"We believe that the invitation should be extended at this stage," he wrote.

"It will become the Allies' adequate response to Russia's constant escalation of the war it has unleashed, the latest demonstration of which is the involvement of tens of thousands of North Korean troops and the use of Ukraine as a testing ground for new weapons," Sybiha added.

"I urge you to endorse the decision to invite Ukraine to join the Alliance as one of the outcomes of the NATO Foreign Ministerial Meeting on 3-4 December 2024," he wrote.