Yesterday the military alliance declined to set a timeline for Ukrainian accession, angering Kyiv.
Ukrainian President Volodymyr Zelenskyy has appeared alongside NATO Secretary General Jens Stoltenberg and G7 leaders at this year's NATO summit, thanking the military alliance for its support.
He declared the pivotal meeting "an important victory" for his country's security.
Zelenskyy's upbeat remarks came after the NATO allies declined to commit to a timeline for Ukraine's accession.
However, steps were made to formalise security guarantees and assurances from major leaders including US President Joe Biden that "Ukraine's future is in NATO".
At a press conference this morning, Zelenskyy confirmed that, while no timeline has been set, NATO would not require Ukraine to create a full action plan before issuing a membership invitation in the future.
This could greatly ease its path to joining, though some allies remain reluctant to admit Kyiv.
"I would like to extend words of gratitude to you for this important step," Zelenskyy said. "Even during the full-scale war against Russia, Ukraine continues to conduct reform."
"We highly appreciate the recognition that Ukraine will not need an action plan on its way to NATO," he added.
Zelenskyy acknowledged other allies' concerns about escalating tensions with Russia, calling this justified while the fighting continues.
Stoltenberg, meanwhile, confirmed NATO has agreed to set up "a multi-year programme of assistance" and remove the membership action plan requirement, reaffirming that "Ukraine will become a member of NATO".
He said the agreement will help Ukraine transfer from Soviet-era military assets to be fully interoperable with other allies, a crucial element of the alliance.
Also being established is a new NATO-Ukraine Council, a permanent body where the 31 allies and Kyiv can hold consultations and emergency meetings.
The council is part of NATO's effort to bring Ukraine as close as possible to the military alliance before it joins.
On Tuesday, NATO leaders said in their communique summarising the summit's conclusions that Ukraine can join “when allies agree and conditions are met."
In the interim, the alliance's top members are planning to ratify a major package of long-term security guarantees.
White House European Affairs Adviser Amanda Sloat told reporters that the multilateral plan, which will be signed by G7 leaders today, will send a "significant signal" to Russia that "time is not on its side".
The framework is designed to provide for Ukraine’s long-term security.
US President Joe Biden and other G7 leaders – from the UK, France, Canada, Germany, Italy and Japan – will join Zelenskyy at the end of the Nato summit on Wednesday to announce this package of security guarantees.
"We are going to fight for this, security guarantees for Ukraine on the road to (membership of) NATO", said the Ukrainian president on his arrival in Vilnius, which began on Tuesday.
On the first day of their meeting, NATO leaders promised that "the future of Ukraine" was "in NATO".
According to the British Foreign Office, the G7 will “set out how allies will support Ukraine over the coming years to end the war and deter and respond to any future attack."
The ministry added that the framework marks the first time that this many countries have agreed to a "comprehensive long-term security arrangement of this kind with another country”.
Zelenskyy has pushed hard for NATO membership in private and in public, calling the lack of a timeline "absurd".
He told a crowd in Vilnius yesterday that membership would benefit both parties.
"NATO will make Ukraine safer, Ukraine will make NATO stronger," he said.
However, Zelenskyy has expressed thanks for new promises of military hardware from key NATO allies, including hundreds of millions of euros in supplies from Germany and new long-range "Scalp" missiles from France.