"Ukraine has urgent needs," Jens Stoltenberg said as the ministers met in Brussels. "Any delay in providing support has consequences on the battlefield as we speak. So we need to shift the dynamics of our support."

"We must ensure reliable and predictable security assistance to Ukraine for the long haul so that we rely less on the voluntary contributions and more on NATO commitments, less on short-term offers and more on multi-year pledges," he said.

Officials said NATO's secretary general has proposed creating a 100-billion-euro ($108 billion) fund to help arm Ukraine in its fight with Russia over five years.

That could help insulate the flow of weaponry to Ukraine following a potential return of Donald Trump to the White House after US elections in November.

"Moscow needs to understand that they cannot achieve their goals on the battlefield and they cannot wait us out," Stoltenberg said, without giving details of his proposal.

- Major shift -

The plan has support from Ukraine's staunchest supporters such as Poland and the Baltic states.

But others caution there are many questions on where financing would come from and the plan could change dramatically by the time NATO holds its next summit in Washington in July.

Belgium's foreign minister, Hadja Lahbib, said the meeting would discuss the "feasibility" of the proposal that envisions NATO members contributing according to the size of their economy.

"But it is dangerous to make promises that we cannot keep," she said.

Germany's Foreign Minister Annalena Baerbock backed setting up "long-term structures" to support Ukraine, but warned against "juggling in the air" vague figures.

The plan from Stoltenberg would also see a NATO mission take more control of coordinating arms supplies to Kyiv from a US-led grouping that currently helps oversee support.

The move would mark a major shift for the Western military alliance, which has so far refused as an organisation to send weapons to Ukraine for fear it would drag NATO closer to a conflict with Russia.

Hungary -- the friendliest country towards Russia in NATO -- said it would not support any proposal that might "draw the alliance closer to war".

- 'Vital that Ukraine wins' -

Stoltenberg's pitch comes as Ukraine's forces are struggling to hold back Russia in the face of dwindling supplies from Kyiv's Western backers.

A $60-billion US funding package is currently stalled in Congress but there are hopes lawmakers could move to pass it in the coming weeks.

Ukraine's Foreign Minister Dmytro Kuleba arrived in Brussels more focused on the short-term need for air defence in the face of a surge in Russian missile bombardments.

"Ukraine is currently the only country in the world that defends itself against ballistic missile attacks almost every day," he wrote on the X social media platform after meeting his Polish counterpart.

"This means that all Patriot batteries available around the world that can be provided to Ukraine must be delivered to Ukraine as soon as possible. There is no more important place for them."

The meeting in Brussels comes as NATO readies to mark on Thursday its 75-year anniversary since it was founded in the wake of World War II to face off against the threat of the Soviet Union.

"As we celebrate NATO's achievements, we do not rest upon them," Stoltenberg said.

"Europe now faces war on a scale we thought was resigned to history."

On the sidelines of the meeting, NATO foreign ministers were also expected to discuss the race to replace Stoltenberg, whose decade-long tenure ends in October.

The frontrunner to succeed him is Dutch premier Mark Rutte, though Romanian President Klaus Iohannis has launched a surprise challenge against him.

Diplomats said Rutte has the support of some 90 percent of NATO countries, but Hungary and Turkey remain holdouts blocking a swift nomination ahead of the summit.