- Speaking to reporters ahead of an informal meeting of NATO foreign ministers in Oslo, Norway, Stoltenberg said all allies agreed that "NATO's door is open for new members."
- Long-term support for Ukraine will be discussed during the Thursday meeting, but Stoltenberg expects a multiyear plan to align Ukraine with NATO standards and protocols to be established at the formal July summit in Vilnius, Lithuania.
NATO Secretary-General Jens Stoltenberg said Thursday that all NATO allies agree that Russia cannot prevent Ukraine's eventual membership in the military alliance.
Speaking to reporters ahead of an informal meeting of NATO foreign ministers in Oslo, Norway, Stoltenberg said all allies agreed that "NATO's door is open for new members."
"All allies also agree that Ukraine will become a member of the alliance, and all allies agree that it is for the NATO allies and Ukraine to decide when Ukraine becomes a member," he said.
"It is not for Moscow to have a veto against NATO enlargement, but most importantly, all allies agree that the most urgent and important task now is to ensure that Ukraine prevails as a sovereign, independent nation. President [Vladimir] Putin and Russia must not win this war."
Stoltenberg also called for action beyond the end of the Russia-Ukraine war to guarantee Ukraine's security, in order to ensure that "history doesn't repeat itself" and that the "pattern of Russian aggression against Ukraine" comes to an end.
Long-term support for Ukraine will be discussed at the Thursday meeting in Oslo, but Stoltenberg expects a multiyear plan to align Ukraine with NATO standards and protocols to be established at the formal July summit in Vilnius, Lithuania.
Ukrainian President Volodymyr Zelenskyy welcomed Stoltenberg's support and reiterated that Ukraine is hoping to receive a formal NATO invitation to join.
"What is very important is our future in the EU and Ukraine is ready to be in NATO, we are waiting for when NATO will be ready to host and to see and to have Ukraine," he told reporters outside of the European Political Community Summit in Moldova on Thursday.
"I think security guarantees are very important, not only for Ukraine, [but] for our neighbors, for Moldova, because of the Russian aggression in Ukraine and potential aggression for other parts of Europe."
Asked about the potential end of the war, Zelenskyy said the conflict will only cease if Ukraine wins, adding that "Russia can stop this war earlier, they can go out to their independent territory from our territory."
NATO members continue to provide substantial military support for Ukraine's war effort in the form of ammunition and training. The Pentagon on Wednesday announced a new weapons package worth $300 million, comprised of artillery and anti-armor defenses, as well as ammunition.
The White House said Putin has shown "zero inclination" to abandon its war effort as the conflict approaches its 500th day, with the Ukrainian capital of Kyiv suffering an aerial bombardment in recent days and drone strikes hitting Moscow.
"I think this week as you have all seen, Russia has continued to wage just a brutal, completely unprovoked war against Ukraine," National Security Council spokesman John Kirby told a White House press briefing on Wednesday.
The Russian Embassy in London did not immediately respond to a request for comment when contacted by CNBC on Thursday.
In early April, Finland officially became the 31st member of NATO — the military alliance predicated on the treaty that an attack on one member nation is an attack on all.
Authorities in Helsinki decided in the wake of Russia's full-scale invasion of Ukraine in February 2022 that historically neutral Finland, which shares an 832-mile border with Russia, was no longer safe and would benefit from the protection offered by NATO membership.
Sweden applied to become a member at the same time as Finland, but its accession has been held up by two NATO members — Turkey and Hungary.
Stoltenberg told reporters on Thursday that he will shortly be heading to Ankara to court Turkey's sign-off on Sweden's accession, while Finnish Foreign Minister Pekka Haavisto said that the ratification process "could and should" happen before the NATO summit in Vilnius next month.