Zelenskiy also reiterated demands for security guarantees if Ukraine, which has been invaded by Russia, is not given membership of the alliance in the near future.

"There is every reason for a political invitation for Ukraine to join the Alliance," he wrote on the Telegram messaging app.

He said there was "a full understanding of the security guarantees for Ukraine until the moment of accession" but gave no further details.

Kyiv has in recent weeks pressed the North Atlantic Treaty Organization increasingly hard over its membership bid and over its demands for security guarantees as the alliance prepares for the July 11-12 summit in Vilnius.

Defence Minister Oleksii Reznikov said last week he expected Kyiv to receive a clear signal and "formula" for it to become a member. Foreign Minister Dmytro Kuleba called on Tuesday for "crucial political decisions" to be made at the summit.

Andriy Yermak, head of the presidential staff, said last week the failure of the alliance to deliver a "strong" decision at the summit would demoralise Ukrainians and that Kyiv had shown it was ready to join with its fighting on the battlefield.

Zelenskiy has also said he recognises it would be impossible to join while Russia's war in Ukraine is still raging.

While Ukraine wants to join as quickly as possible, the alliance is divided over how fast that step should be taken.

Western governments such as the United States and Germany are wary of moves they fear could take the alliance closer to entering an active war with Russia, which has long seen NATO's expansion into eastern Europe as evidence of Western hostility.