"NATO must and will do more to help Ukraine," Rutte, who took over at the helm of the alliance this month, told journalists.

"Russia continues to carry out massive strikes against Ukraine's critical energy infrastructure. Ukraine could be facing its toughest winter since the full-scale invasion began."

US President Joe Biden had planned to host a gathering of leaders in Germany at the weekend to marshall support for Kyiv in what Rutte called an "extremely important meeting".

But the White House on Tuesday announced Biden had to postpone his trip to oversee preparations as monster Hurricane Milton bears down on Florida.

Moscow has targeted Ukraine's electricity grid with a ferocious air campaign ahead of the third full winter of all-out war.

Rutte, who visited Kyiv last week, admitted that the situation on the battlefield was "difficult" for Ukraine as Russia advances in the east of the country.

But he said the gains for Moscow were "coming at a considerable cost".

"We have to also take into account that the Russian losses are huge. They now stand at about, as far as we know, 1,000 killed and wounded each day," Rutte said.

"That is on top of a total of 500,000 already killed or wounded."