Ukrainian President Volodymyr Zelensky has knuckled down on his plea for Western aircraft after securing commitments for tanks, air defence and precision missiles.

But allies insist they are scrambling to ensure his forces have the ammunition and heavy weaponry they need on the ground to push back renewed Russian offensives.

Ukrainian Defence Minister Oleksiy Reznikov tweeted he was focused on building an "aviation platform", winning more promises of tank supplies and ensuring ammunition stocks.

He flashed a handkerchief with a picture of a jet on it as he entered a meeting with representatives of more than 50 nations supporting Kyiv at NATO headquarters in Brussels.

"This has become a grinding war of attrition and therefore it's also a battle of logistics," NATO Secretary General Jens Stoltenberg said.

"This is a huge effort by allies to actually be able to get in the ammunition, the fuel, the spare parts, which are needed."

Ukraine's Western supporters -- spearheaded by the United States -- have already supplied billions of dollars of arms to help Kyiv hold Moscow back.

- 'Hold and advance' -

Now, just under a year into the war, Stoltenberg said Russian President Vladimir Putin appears to have started a long-awaited new offensive in east Ukraine.

"We will support Ukraine's fight for freedom over the long haul, and help Ukraine hold and advance during the spring counter-offensive," US Secretary of Defense Lloyd Austin said.

"We must intensify our focus. Ukraine has urgent requirements to help it meet this crucial moment."

A senior US official said the priority was on getting Ukraine air defence, artillery, ammunition and armoured vehicles.

Norway's government became the latest to join a group of nations promising Leopard 2 tanks by offering eight.

The fighting is consuming vast quantities of ammunition, straining stockpiles and industries on both sides of the confrontation.

Stoltenberg warned that Kyiv's current rate of expenditure was "many times higher" than the output in NATO countries.

Allies continue to raid their shelves for the rounds -- especially 155-millimetre shells -- that Ukraine is firing by the thousands each day.

NATO is scrambling to get its factories to pump out more, and allies are eyeing plans for joint weapons purchases, higher defence spending and longer-term contracts.

German Defence Minister Boris Pistorius said Berlin had signed a deal with manufacturer Rheinmetall to restart production of ammunition for Gepard air defence guns sent to Ukraine.

- Jets not 'most urgent' -

Zelensky issued a powerful call during a trip to London, Paris and Brussels last week for NATO members to send fighter planes and longer-range missiles.

The Ukrainian leader won a commitment from Britain to train pilots but did not get any firm promises that his forces will get Western planes.

But the senior US official said that sending jets was "not something we're talking about around that table, right now, today".

Slovakia has said it is willing to discuss sending Soviet MIG-29 planes to help replace losses to Ukraine's current stocks.

Dutch Defence Minister Kajsa Ollongren said Kyiv had requested US-made F-16 jets from the Netherlands.

"We have to debate this with our partners, also with the United States, and we have to think about feasibility," she said.

Stoltenberg insisted "the issue of aircraft is not the most urgent issue now, but it is an ongoing discussion".

"The urgent need now is to deliver what has already been promised," he said.

del/imm

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