"Ukraine continues to work actively with all NATO allies to convince them that the time for clarity on Ukraine's membership in the Alliance has come," Foreign Minister Dmytro Kuleba tweeted after speaking by phone with NATO Secretary General Jens Stoltenberg.

The future relationship between Ukraine and NATO is expected to be a key question on the agenda of a NATO summit in Vilnius on July 11-12.

Speaking in parliament on Wednesday, Zelensky argued that Kyiv's battle-hardened troops would help strengthen NATO -- not weaken it -- when Ukraine will be "victorious."

"We are now a recipient of security assistance," Zelensky said.

"But a victorious Ukraine will be a donor of security for our region, for the whole of Europe, for the whole world."

Stoltenberg said this week it was crucial to keep supporting Ukraine against Russia's invasion and that NATO allies would thrash out a path to Kyiv's membership of the alliance.

Russian leader Vladimir Putin has repeatedly raged about NATO's eastward expansion, accused NATO members of taking part in the Ukraine conflict by donating arms to Kyiv and said the West planned to break up Russia.

Even Zelensky himself acknowledged this month that Ukraine would not be able to join NATO before the end of the Russian invasion.

Russia's invasion of Ukraine in February last year has galvanised the Western military alliance, set up almost 75 years ago, to face off against the Soviet Union.

But members of the military bloc are split over Ukraine, with Stoltenberg saying all members agree to stick by a 2008 pledge that Ukraine will become a member at some undefined point.