President Zelenskyy and Ukrainian defence chiefs told a UK newspaper that Moscow is planning a major push that could include a renewed attempt to take the capital Kyiv.
Ukraine's president and senior defence chiefs have predicted that Russia will launch a new offensive early next year that could include a second attempt to take the capital Kyiv.
Their warnings came as Western allies stepped up their support for Ukraine with additional funding and military training.
Moscow's new offensive could happen as soon as January, Volodymyr Zelenskyy, General Valery Zaluzhniy and General Oleksandr Syrskiy were quoted as saying in interviews with The Economist magazine on Thursday.
Officials said the push could be launched from the eastern Donbas area, the south or neighbouring Belarus, and could include another ground assault on Kyiv, which Moscow failed to capture early in the invasion.
"The Russians are preparing some 200,000 fresh troops. I have no doubt they will have another go at Kyiv," Zaluzhniy was quoted as saying.
Ukrainian Defence Minister Oleksiy Reznikov also said in remarks published in The Guardian on Thursday that evidence was mounting that Russia planned a broad new offensive.
He speculated this could occur in February when half of the 300,000 troops conscripted by Russia in October to support the war would complete training.
“The second part of the mobilisation, 150,000 approximately ... do a minimum of three months to prepare. It means they are trying to start the next wave of the offensive probably in February, like last year. That’s their plan,” Reznikov told The Guardian.
Both sides have ruled out a Christmas truce and there are currently no talks aimed at ending the conflict, Europe's largest since World War Two.
EU and US agree more aid for Ukraine
European Union leaders agreed on Thursday to provide €18 billion in financing to Ukraine next year and hit Moscow with a ninth package of sanctions.
The US Senate passed a bill for a record $858 billion defence budget next year -- authorising $45 billion more than proposed by President Joe Biden. The bill, which Biden is expected to quickly sign into law, provides Ukraine at least $800 million in additional security assistance in 2023.
Ukraine has repeatedly urged its allies to send more air defences to counter Russian missile bombardment including against its energy infrastructure.
Russia has fired barrages of missiles on Ukraine's energy infrastructure since October, disrupting power supplies and leaving people without heating in freezing winter conditions.
Russia continues pounding east and south
Over the past 24 hours, Ukrainian troops repelled Russian infantry attacks in a number of locations in the Donetsk region including Bakhmut and Soledar, Ukraine's general staff said on Friday.
Russian military carried out 23 air strikes and four missile strikes as well as 78 bombardments using multiple rocket launchers, it said.
Ukraine's military General Staff said Russia's main focus remained on the eastern cities of Bakhmut and Avdiivka, but that it was also trying to get a stronger foothold in the southern region of Zaporizhzhia.
It said that on December 14, Ukrainian forces destroyed a quantity of military equipment in the town of Tokmak, the Zaporizhzhia region, wounding about 180 Russian troops.
Russia's state TASS news agency reported on Friday that at least eight people were killed and 23 injured by Ukrainian shelling in the village of Lantrativka in the Russia-controlled Luhansk region of Ukraine.
Reuters was unable to immediately verify the battlefield accounts.
Earlier this week, Reuters reported that the United States is finalising plans to offer Ukraine the Patriot missile defence system -- one of the most advanced systems, and one which could require months of training.
The Kremlin said the United States was getting "deeper and deeper into the conflict" and that Patriot systems would be legitimate targets. Russia's foreign ministry said on Thursday this applied to all weapons supplied by the West.