NATO foreign ministers meet on Wednesday to discuss how to put military support for Ukraine on a long-term footing, including a proposal for a 100 billion euro ($A164 billion) five-year fund and a plan seen as a way to “Trump-proof” aid for Kyiv.

The proposals by NATO Secretary General Jens Stoltenberg would give the Western alliance a more direct role in coordinating the supply of arms, ammunition and equipment to Ukraine as it fights Russia’s invasion, diplomats say.

The plans will be discussed during a two-day meeting in Brussels that will celebrate the 75th anniversary of the founding of the North Atlantic Treaty Organisation and prepare for a summit of alliance leaders in Washington in July.

The meeting will provide insight into how far Ukraine’s European allies are willing to go to support Kyiv’s war effort as a military aid package for Ukraine worth some $US60 billion remains stalled in the US Congress.

Under the plans, NATO would take over some co-ordination work from a US-led ad-hoc coalition known as the Ramstein group – a move designed in part to guard against any cut in US support if Donald Trump returns to the White House, diplomats said.

Until now, NATO as an organisation has focused on non-lethal aid for Ukraine out of fears that a more direct role could trigger an escalation of tensions with Russia. Its members have provided billions of dollars in arms on a bilateral basis.

Diplomats said there was a growing view within NATO that it was time to put military aid to Ukraine on a more sustainable footing and NATO was best placed to do that.

Some said threats by Russian President Vladimir Putin that he would regard various steps taken by NATO allies as escalatory – such as providing tanks and other advanced weapons systems – had not led to retaliation against them.

US Secretary of State Antony Blinken, who will attend the Brussels meeting, said that NATO was looking at measures that could serve as the “necessary bridge” to membership of the alliance for Ukraine.

NATO has stated that Ukraine cannot join while it is at war with Russia but that it will become a member at some point.

NATO declined to comment in detail on Stoltenberg’s proposals but a NATO official said the ministers would “discuss the best way to organise NATO’s support for Ukraine, to make it more powerful, predictable and enduring”.

Diplomats cautioned that discussions on the proposal were at an early stage and it was unclear whether the 100 billion euro figure would be accepted or how it would be financed. NATO decisions require consensus among the alliance’s 32 members.

The proposal comes as British Foreign Minister David Cameron urged NATO allies to bolster defence spending and production in support of Ukraine amid the ongoing Russian invasion.

“Allies need to step up and spend more on defence in the face of continued Russian aggression and a more dangerous world,” Cameron will say in a speech on the occasion of 75 years of NATO history since its founding April 4, 1949.

“With Ukraine closer to NATO than ever, we must sustain the critical support Ukraine needs to win the war.”

The Brussels meeting will also seek a new leader to succeed Stoltenberg, who has been in post for nearly 10 years.

Dutch Prime Minister Mark Rutte has the backing of a some 90 per cent of NATO members for the job – including the United States, France, Britain and Germany – according to diplomats.

But he faces opposition from Hungary – which objects to his criticism of Prime Minister Viktor Orban’s government – and a late challenge from Romanian President Klaus Iohannis.

Some diplomats had hoped to choose Stoltenberg’s successor at the Wednesday’s meeting but they said more time would now be needed.