The United States, Britain and global allies are preparing to unveil new security assurances for Ukraine designed to protect the country from future attacks while Kyiv strives towards membership of the alliance.
The prospect of long-term protection from members of the world's most powerful military bloc as it meets at a summit in Vilnius comes a day after President Volodymyr Zelenskiy decried as "absurd" NATO's refusal to offer an invite or timetable for Ukraine's entry into the alliance.
Ukraine has been pushing for rapid NATO membership while fighting a Russian invasion unleashed in February 2022 that has killed tens of thousands and displaced millions.
Instead, a declaration by the G7 world's most industrialised countries "will set out how allies will support Ukraine over the coming years to end the war and deter and respond to any future attack", a British government statement said.
In practice, this would come as bilateral agreements with Kyiv on long-term military and financial aid to keep Ukraine's army and economy running.
The G7 is made up of the US, Germany, Japan, France, Canada, Italy and Britain.
Swallowing his disappointment over the lack of a membership timetable, Zelenskiy on Wednesday said the results of the summit in Vilnius had been good overall and welcomed a flurry of announcements of new military aid from allies.
Nevertheless, Zelenskiy pressed for more and said he would raise Ukraine's need for long-range weapons at a meeting with US President Joe Biden at the summit.
"We can state that the results of the summit are good, but if there was an invitation, they would be ideal," Zelenskiy said.
White House national security adviser Jake Sullivan said Biden would be open with Zelenskiy about the rationale for NATO's decision on membership.
"He knows that President Zelenskiy has strong views and isn't afraid to express those views," Sullivan told MSNBC.
"And he, President Biden, also is very straightforward and honest and candid with President Zelenskiy."
NATO, an alliance built around mutual security guarantees - the concept that an attack on one is an attack on all - has carefully avoided extending any firm military commitments to Ukraine, worried that would risk taking it closer to a full-on war with Russia.
Ukraine is deeply suspicious of any less-binding security "assurances", given Russia's invasion already trampled the so-called Budapest Memorandum under which international powers committed to keeping the country safe in exchange for Kyiv giving up its Soviet-era nuclear arms.
Speaking alongside Zelenskiy, NATO secretary general Jens Stoltenberg said Ukraine was closer to the alliance than ever before and brushed aside new warnings from Russia about the consequences of supporting Ukraine.
"Ukraine has the right to choose its own path", Stoltenberg said, adding "it is not for Moscow to decide".
The security assurances for Ukraine had to be "credible", he said, to deter Russia from future attacks.
"Of course guarantees, documents, council meetings are important but the most urgent task now is to ensure enough weapons for Ukrainian President Zelenskiy and his armed forces," Stoltenberg said.
British Prime Minister Rishi Sunak said the security arrangements for Ukraine were not designed to be a substitute for full NATO membership.
On Wednesday, Zelenskiy was holding bilateral meetings with the US, Canada, Germany, Britain, Japan and the Netherlands on the sidelines of the second day of the NATO summit in Vilnius to secure more arms for his counteroffensive.
The first sitting of a new NATO-Ukraine Council was also due on Wednesday, a format designed to tighten co-operation between Kyiv and the 31-nation alliance.
NATO says Ukraine would not be allowed in while at war with Russia, with Washington and Berlin warning against any moves that could put the alliance in direct conflict with Moscow.
Backers of Ukraine's swift NATO accession in eastern Europe and elsewhere have bristled at what they consider a disappointing outcome of the first day of the summit.
Russia, which says NATO's eastward expansion is an existential threat to its own security, swiftly lashed out.
Dmitry Medvedev, the deputy secretary of Russia's powerful Security Council chaired by President Vladimir Putin, said increasing military assistance to Ukraine by NATO was bringing a World War III closer.