The meeting at the Elysee Palace will be a chance for participants to "reaffirm their unity as well as their determination to defeat the war of aggression waged by Russia in Ukraine", the French presidency said Sunday.

German Chancellor Olaf Scholz and Polish President Andrzej Duda will be among some 20 European heads of state and government present at the conference, which will be opened by a video address from Ukrainian President Volodymyr Zelensky.

Other states will be represented at ministerial level, with Foreign Secretary David Cameron travelling to Paris for Britain.

The United States and Canada will be represented by senior diplomats but almost all the participants are from Europe with no sign of Chinese or Indian representation.

Slovak Prime Minister Robert Fico, whose government is seen as more sympathetic to Russia, will also attend.

According to the French presidency, the meeting will seek to "examine all means to support Ukraine effectively".

Western officials acknowledge that Russia risks gaining the upper hand in the conflict in 2024 as Ukraine runs out of weapons and ammunition.

Ukrainian Defence Minister Rustem Umerov said on Sunday that half of Western military aid pledged to Kyiv is delivered late, lamenting that "commitment does not constitute delivery."

A French presidential official, who asked not to be named, said the meeting needed to contradict any "impression that things are falling apart" after Ukraine's setbacks on the battlefield.

"We want to send a clear message to (Russian President Vladimir) Putin that he will not prevail in Ukraine," said the official. Even if new aid announcements are not planned, participants will examine ways to "do things better and more decisively."

For Macron, who even before the Russian invasion was preaching the need for Europe to find strategic autonomy in security matters, the conference is a vital chance to show Europe can stand more alone.

There are growing doubts about the viability of long-term American backing for Ukraine as a new aid package struggles to find legislative approval and Donald Trump eyes a return to the presidency in elections later this year.