Kyiv, Ukraine - Ukraine's Volodymyr Zelensky spoke with US envoys Steve Witkoff and Jared Kushner in the midst of his spat with President Donald Trump Sunday, saying "a lot depends on America" as he earlier warned Washington not to side with Moscow in Europe's worst conflict since WWII, saying it would be a "historic mistake."

The wartime leader spoke to the US officials as both Russia and Ukraine hit each other's energy sites, with Moscow leaving thousands without power and Kyiv carrying out the largest drone attack on Saint Petersburg since the start of the 2022 war.

Trump and Zelensky have clashed as the US leader blocked new sanctions on Russia and struck a diesel deal with Moscow, fuelling fears in Kyiv and Europe that the White House was steering towards Moscow.

After speaking to Trump's business partner Witkoff and son-in-law Kushner, Zelensky said "a lot depends" on the US position in the war but that "it is clear that there are many things that matter to all of us and that this war must be brought to an end."

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Ukraine, he said, was ready to work "constructively" and "honestly" and that: "We expect exactly this approach from all our partners – both from the Europeans and, of course, from the American side."

He said he discussed deliveries of US Patriot air defence systems, as Kyiv struggles to counter Russian missiles.

Zelensky earlier told NBC it would be a "historic mistake" if Washington formally supported Russia and that he hoped Trump would "change his decisions."

But he also said he was "thankful" the US resumed intelligence sharing after a pause that left his country vulnerable to Russian missile strikes.

A US-led push to end the Ukraine-Russia war has so far not led to a breakthrough and Trump has in the past grown frustrated with both Zelensky and Russia's Vladimir Putin because of their lack of progress.

Zelensky spoke to the American officials as he accused Moscow of breaking Trump's "energy ceasefire" 76 times and warned Moscow planned to deprive Ukrainians of heat and electricity before winter.

Russian strikes left "tens of thousands" without power in several regions, he said, with Ukrainian officials reporting three people had been killed.

Ukraine's army launched drones at Putin's hometown of Saint Petersburg on Sunday night, setting an oil refinery ablaze and killing one person, Moscow said.