Ukrainian President Volodymyr Zelenskiy meets NATO leaders on Wednesday after they declared his country's future lay inside the alliance but rebuffed his call for a timeline to membership.
He will join the NATO leaders on the second day of their summit in Vilnius for an inaugural session of the NATO-Ukraine Council, a body established to upgrade relations between Kyiv and the 31-member transatlantic military alliance.
Zelenskiy will also meet separately with US President Joe Biden as he seeks more arms and ammunition from the US and other NATO nations to fight the war triggered by Russia's invasion of Ukraine in February last year.
The US, Britain, France and Germany are expected to issue assurances to Kyiv of long-term security support in the form of advanced weaponry, training and other military aid, possibly soon after the summit ends, according to officials.
Other countries would then join this framework with their own bilateral commitments, officials say.
At a rally in Vilnius on Tuesday, Zelenskiy expressed disappointment that NATO had not offered a timeline to membership - a prospect he had earlier branded "absurd".
"NATO will make Ukraine safer, Ukraine will make NATO stronger," he told a crowd of thousands of people in Vilnius, many waving Ukrainian flags, as snipers stood guard on rooftops.
He pivoted to more emollient language towards NATO allies on Tuesday night.
"Our defence is a top priority, and I am grateful to our partners for their willingness to take new steps," he wrote on Twitter.
"More weapons for our warriors, more protection of life for the whole of Ukraine! We will bring new important defence tools to Ukraine."