Russia is preparing a new offensive against Ukraine but Kyiv has a clear battlefield plan of its own, President Volodymyr Zelenskiy says.
Speaking a day after the second anniversary of Russia's invasion of Ukraine, Zelenskiy said the planned new offensive against Ukraine would start in late May or the northern summer.
He said it was vital Kyiv and its Western allies remained united and reiterated that Ukraine's victory depended on continued Western support.
"We will prepare for their assault," Zelenskiy told reporters in Kyiv on Sunday.
"Their assault that began on October 8 has not brought any results, I believe.
"We, for our part, will prepare our plan and follow it."
Zelenskiy said that 31,000 Ukrainian soldiers had been killed since February 2022, giving the first official toll in more than a year.
The Russian foreign ministry rejected the Ukraine figure as untrue.
Zelenskiy said that troop rotations would be critically important for the war effort and emphasised that Ukraine needed to better prepare its reserve forces.
A New York Times report in August cited United States officials as putting the Ukrainian death toll at close to 70,000.
The same report said as many as 120,000 Russian troops had died during the war.
The tallies could not be independently verified.
Both Russia and Ukraine have often underestimated their military casualties in the war and exaggerated the losses they claim to have inflicted upon each other.
Two years into the war, Moscow's troops bear down along the sprawling 960km front line in Ukraine's east and south and problems pile up from shortages of artillery shells and the need for longer-range missiles to a lack of fresh troops.
Zelenskiy said he was confident US Congress would approve a major new batch of military and financial assistance and that Ukraine needed that decision within a month.
The Ukrainian war effort depended on Western support, he said, adding that the European Union had only supplied 30 per cent of the million ammunition shells promised.
Russia secured its biggest battlefield gains since May 2023 this month as it captured the town of Avdiivka, which Ukrainian troops retreated from to avoid being surrounded.
President Vladimir Putin said on Tuesday that Russian troops would push farther into Ukraine to build on their success in Avdiivka and on Sunday Russian defence ministry said its forces had taken more advantageous positions near the town.
On Ukraine's battlefield intentions, Zelenskiy said Kyiv had a clear plan to counter Russian forces, but that he would not disclose details that could compromise it.
"There is a plan - the plan is clear," he said.
"I can't tell you the details."
Kyiv's troops conducted a much-vaunted counteroffensive in 2023 but were unable to pierce Russia's defensive lines.
Zelenskiy said replacing his popular armed forces chief in a dramatic military shake-up this month was part of his military strategy that would remain under wraps.
The Ukrainian leader said earlier that Kyiv's plans for 2023's counteroffensive had ended up "on a desk in the Kremlin" before the operation had even begun but did not say how.
Kyiv hopes to hold a summit in Switzerland to discuss its vision for peace with its allies, he said, adding that the peace blueprint would later be presented to Russia.
"I hope it will take place this spring," he said.
"We must not lose this diplomatic initiative."
