President Volodymyr Zelensky will present his "victory plan" for Ukraine to NATO defence ministers gathering Thursday in Brussels, under the long shadow of next month's US elections.

Underscoring his plea for ramped-up Western support, Zelensky will attend the Alliance talks after also presenting his much-touted proposal at an EU leaders' summit taking place across town from NATO.

NATO chief Mark Rutte will hold a joint press conference with Zelensky at 6:20 pm (1620 GMT), wrapping the first of two days of talks between NATO's 32 member states.

While calling it a "strong signal," the secretary-general cautioned Wednesday he was not endorsing Zelensky's "whole plan" -- which calls first and foremost for an immediate invitation to join the US-led alliance, a plea widely seen as unrealistic.

NATO countries have declared Ukraine to be on an "irreversible path" to membership. 

But the United States and Germany have led opposition to immediate entry, believing it would effectively put the alliance at war with nuclear-armed Russia.

Washington's ambassador to NATO, Julianne Smith, hammered home that stance Wednesday, saying: "We are not at the point right now where the alliance is talking about issuing an invitation in the short term."

The US position is unlikely to shift whether Donald Trump or Kamala Harris wins the White House on November 5 -- though there are fears a second Trump term could upend the support Ukraine receives from NATO's biggest power.

Insiders agree the elephant in the room at the NATO talks will be the contest playing out across the Atlantic.

"We are in a kind of waiting mode," summed up one NATO diplomat.

- 'Very difficult period' -

Pressed on the membership question, Rutte reiterated NATO's party line, saying: "I cannot today now exactly sketch out what the path will be, but I am absolutely confident that in the future, Ukraine will join us."

But Ukraine's allies are well aware that time is of the essence.

With Kyiv losing new territory almost daily in its eastern Donbas region, the outlook on the battlefield is bleak.

"It's a very difficult period, the worst since the beginning of the invasion," said a second NATO diplomat, speaking on condition of anonymity.

In addition to membership, Zelensky's plan rejects any territorial concessions and calls for Western allies to lift restrictions on using donated long-range weapons to target Russian military sites.

According to Zelensky, an annexe -- so far shared with the United States, Britain, France, Italy and Germany -- involves deploying a "non-nuclear strategic deterrence package" on Ukrainian territory to discourage future Russian attacks.

None of the proposals have so far earned public backing from Western capitals.

For NATO in the meantime, Rutte stressed the focus was on keeping "massive military aid moving into Ukraine".

"We are working very hard to make sure they can prevail," he said. "And to make sure that if ever one day Zelensky and his team decide to discuss with Russia how to end this, that he will do this from a position of strength."

For a third NATO official, the setbacks inflicted on Russian President Vladimir Putin since the invasion are already sufficient to justify seeking a negotiated outcome -- rather than letting the war drag on indefinitely.

- 'Various ways to define victory' -

"There are various ways to define victory or to define defeat," they said. "He has lost already because his initial aim was to capture Kyiv, to kick out the government, to send Zelensky in exile and to install a puppet regime."

On the eve of the NATO meeting, German Chancellor Olaf Scholz called for exploring ways to end the war -- potentially including talks with Putin.

But according to an alliance diplomat other voices still fear that anything short of an outright victory for Kyiv would spell "disaster" -- ensuring that an emboldened Russia does not stop there.

High hopes were pinned on a meeting of Ukraine's backers including Washington at the Ramstein US air base in western Germany, but the meeting was called off and may not be rescheduled before the US election.

In the meantime, as Russian forces pound its cities and infrastructure, Ukraine is pleading for stepped-up air defence systems -- but no new announcements were expected from NATO on that front.

"I would be surprised if there was a surprise," summed up a diplomat.