President Volodymyr Zelenskiy has called on Ukrainians to remain united, days after a rift emerged between his office and the country's commander-in-chief as the war with Russia grinds on.

The Ukrainian leader, who also said it was not the right time for wartime elections in a speech late on Monday, entreated Ukrainians to strengthen the country and not to be drawn into dangerous infighting that could imperil the war effort.

"Now everyone should think about defending our country. We need to pull ourselves together, avoid unwinding and splitting up into disputes or other priorities," he said. "If there is no victory, there will be no country. Our victory is possible."

Zelenskiy's call came after tensions burst into the open over the weekend between the president's office and his top general Valery Zaluzhnyi, who likened the state of the battlefield with Russia to a stalemate from World War One.

Days later, Zelenskiy rejected the idea of any stalemate in the war, while his foreign affairs adviser said Zaluzhnyi's remarks about the war to The Economist had been "very strange" and could play into Russia's hands.

The idea of a battlefield stalemate is highly sensitive in Kyiv, as it has repeatedly said it is opposed to any negotiations with Kremlin leader Vladimir Putin whose troops, it says, must first be withdrawn from its land.

In another apparent breakdown in communication, Zelenskiy on Friday replaced the head of his Special Operations Forces who said he only learned of his dismissal from media reports and that Zaluzhnyi - his boss - had also been kept in the dark.

The signs of strain come as pressure builds on Kyiv on the frontlines and beyond.

Kyiv is five months into a counteroffensive that has not made a major breakthrough in the heavily defended occupied south and east. Questions are also swirling over the sustainability of Western military aid and Kyiv fears it is entering a second winter of sustained Russian air strikes on its power grid.

ELECTION QUESTION

Some Ukrainian sociologists say polls indicate a darker mood creeping into Ukrainian society, with surveys showing a majority of people do not trust the government or parliament.

Zelenskiy's own ratings remain very high, although they too have dipped since he led Ukraine through the first year of Russia's invasion.

In his nightly speech on Monday, Zelenskiy said all the resources of the state and the full attention of the country were needed for victory and that budget resources should be ploughed into defence, and not repairing streets.

He also told Ukrainians it was "not the time" to hold a presidential election, apparently ending weeks of speculation that Kyiv could try to find a way to hold the vote in March despite it being prohibited by martial law.

"We all understand that now, in wartime, when there are so many challenges, it is absolutely irresponsible to throw the topic of elections into society in a lighthearted and playful way," Zelenskiy said.

If not for martial law, imposed when Russia launched its February 2022 invasion and rolled over every three months, the election would have been due in March, the same month Putin is expected to stand for re-election in Russia and extend his rule.

The election was widely discussed in Ukraine after U.S. Republican Senator Lindsey Graham said it should go ahead despite the war, even as western observers said privately it would undermine unity and be easily exploited by Russia.

"I believe that now is not the right time for elections," Zelenskiy said.