Kyiv had initially requested Australia transfer its retiring Tiger helicopters, but its defence ministry is now asking for American Apaches, Ukrainian ambassador Vasyl Myroshnychenko said.
The Apache request is being made to the US, and not Australia's incoming 29-strong fleet, which it has bought to replace its 22 retiring Tigers.
"There was an interest in Tigers originally, but the position has changed," Mr Myroshnychenko told reporters in Canberra at an event at the European Commission embassy on Monday.
Ambassadors from EU member states and officials from other nations, including Australia, were briefed on the war by the Ukrainian ambassador on the cusp of the fourth anniversary of Russia's invasion, which is on Tuesday.
"This has become a very sad habit for us," EU ambassador Gabriele Visentin said alongside Mr Myroshnychenko, with ambassadors and envoys in Australia meeting on every anniversary to express sustained support.
The Ukrainian ambassador called for more Australian contributions to a NATO-led Ukrainian fund that co-ordinates critical defence purchases for the besieged nation.
Australia has donated more $1.7 billion to Ukraine, including $1.5 billion in military assistance, since the start of the war, but concerns have been raised about the sporadic approach to announcing support.
"We appreciate what we get, don't get me wrong ... Bushmasters have become symbols of support, Australian tanks are there defending Ukrainian democracy - it's just, this war is so brutal," Mr Myroshnychenko said, vowing to raise the issue with Defence Minister Richard Marles on Monday.
"We need your support now more than ever," he said.
The Ukrainian ambassador also raised the alarm over an increasing Russian presence in the Indo-Pacific, revealing Australia's defence and foreign affairs departments had commissioned and received reports into Russian influence in the region.
Mr Myroshnychenko rejected any peace deal with Russia that would cede Ukrainian territory, saying it was about more than just the land.
"It's about the people who live there under the Russian occupation," he said.
"How much torture, rape, total erasure of their identities (is) happening in the occupation?"
