"Some are questioning whether the United States and other NATO allies in truth continue to stand with Ukraine as we enter the second winter of (Russian President Vladimir) Putin's brutality," Blinken said.

"But the answer here today at NATO is clear and it's unwavering. We must and we will continue to support Ukraine."

There are fears that a lack of adequate support from the West -- at a time when it is distracted by the Israel-Hamas war -- could end up forcing Kyiv to seek a compromise with Putin from a position of weakness.

Western officials insist they remain committed and are not pressing Kyiv to negotiate with Moscow even as Ukraine's top general admits fighting has ground to a bloody stalemate.

Ukraine's foreign minister said Wednesday that it won't "back down" in its fight against Russia, despite doubts over US support and minimal progress on the front line.

"We have to continue, we have to keep fighting. Ukraine is not going to back down," Ukraine's top diplomat Dmytro Kuleba told Kyiv's NATO backers in Brussels.

"Our strategic goal, which is territorial integrity within internationally recognised borders as of 1991, remains unchanged," he said.

"The issue here is not just Ukraine's security it is the security and safety of the entire Euro-Atlantic space."

Opposition from hardline Republicans in the US Congress has stalled a new $60-billion package of support and thrown into question the future of Washington's assistance.

"Hopefully the US Congress will also find a solution that will be in the best interests of the American people which is actually to support both Israel and Ukraine," Kuleba said.

- 'Defending Europe' -

"Because you know, the best way to avoid sending your own soldiers into war is to help another country fight its own war."

Ukraine is pushing to join NATO to ensure it is covered by the US-led alliance's protective umbrella.

NATO has vowed Kyiv will join one day but refused to issue a formal invite at a summit this summer due to fears from key powers the United States and Germany that Ukraine's membership could drag them into war with Moscow.

NATO members made recommendations on Wednesday over reforms -- both military and political -- for Kyiv to carry out aimed at helping it get closer to eventually joining the alliance.

Kuleba said that due to the major Western support during the war Ukraine was already becoming "a de facto NATO army in terms of our technical capacity, management approaches and principles".

"Defending Europe without Ukraine is a futile task," he said.

"You cannot do it simply for one simple reason -- we currently have the strongest and the most battle-hardened army in Europe."

Kuleba pushed back at any suggestion that his country should have to cede any of the territory occupied by Moscow to gain NATO membership.

"Somehow it's always easy to advise someone else to give up and make concessions," Kuleba said.

NATO chief Jens Stoltenberg warned that Moscow had amassed a "large missile stockpile" to bombard Ukraine's infrastructure during the winter.

But he insisted that the Kremlin's war on its neighbour was a failure that had left Russia weaker, more isolated and increasingly dependent on China.

"Moscow is mortgaging its future to Beijing," Stoltenberg said.