The alliance's chief, meanwhile, noted that the consent of all 30 members is needed
The presidents of nine NATO countries came together on Sunday to express their support for Ukraine's membership bid and also to urge all allies to "substantially increase" their military support to Kiev.
The statement came two days after Ukrainian President Vladimir Zelensky announced his country's intention to apply for fast-track NATO membership.
"We firmly stand behind the 2008 Bucharest NATO Summit decision concerning Ukraine's future membership," the presidents of the Czech Republic, Estonia, Latvia, Lithuania, North Macedonia, Montenegro, Poland, Romania, and Slovakia said.
At the Bucharest summit, the alliance members welcomed the "aspirations for membership in NATO" of Ukraine and Georgia but didn't provide any time frame for these countries' accession.
"We support Ukraine in its defence against Russia's invasion, demand Russia to immediately withdraw from all the occupied territories and encourage all Allies to substantially increase their military aid to Ukraine," the statement said.
Referring to the impending inclusion of four former Ukrainian regions into the Russian Federation, the leaders said that they would "never" recognize "Russian attempts to annex any Ukrainian territory."
Meanwhile, NATO Secretary General Jens Stoltenberg, commenting on Zelensky's NATO bid, emphasized that "any decision on membership has to be taken by consensus" of all thirty members. Stressing that NATO "has an open door policy," Stoltenberg said that currently the top priority of the bloc is "to support Ukraine," both militarily and financially. He believes that this is also "the best way to respond" to Russia's actions.
Stoltenberg's remarks echoed a statement made earlier by the White House. Speaking on Friday, US National Security Adviser Jake Sullivan claimed that the best way now is to provide Ukraine with "practical" support, while "the process in Brussels should be taken up at a different time."
Ukrainian Deputy Prime Minister Olga Stefanishyna, meanwhile, revealed on Sunday that Kiev's NATO application "is already on its way to Brussels."
Zelensky's announcement of the NATO membership bid came on the same day that Russian President Vladimir Putin signed treaties on the inclusion of two Donbass republics, and Kherson and Zaporozhye Regions, into Russia. Moscow, which considers the enlargement of NATO a direct threat to its national interests and cited Ukraine's potential membership in the alliance as one of the reasons for its military offensive.