"We have strong wording regarding the irreversibility of Ukraine's movement towards NATO. Every step truly brings us closer to membership," Zelensky told a news conference at a NATO summit alongside the alliance's chief Jens Stoltenberg.

"We are doing and will continue to do everything to ensure that the day comes when Ukraine is invited and becomes a NATO member, and I am confident we will achieve this," he said.

Zelensky's reaction was significantly warmer than a year ago at the NATO summit in Lithuania where he was visibly upset that there was not a firmer promise on membership.

NATO, formed in the Cold War, is a collective defense pact in which an attack on one ally is an attack on all.

The United States and Germany have led concerns about quickly bringing Ukraine into NATO, believing it would effectively put them at war with nuclear-armed Russia.

A declaration issued Wednesday at the 75th anniversary NATO summit in Washington said leaders supported Ukraine on "its irreversible path to full Euro-Atlantic integration, including NATO membership."

Russian President Vladimir Putin has cited Ukraine's NATO aspirations as a reason to attack the former Soviet republic, rejecting the idea that the country has a separate historical identity.