Moscow's forces are pressing ahead with an effort to capture the rest of eastern Ukraine's industrialised Donbas region, where its troops have ground forward at what Kyiv says is a great cost.
Ukrainian President Volodymyr Zelenskiy said Russia could draft more troops in 2027 to reach an overall goal of 500,000, part of what he described as a "peripheral mobilisation" targeting Russia's far-flung regions.
"We believe it will not take place in the central cities," he said in comments to reporters released on Sunday.
"But I don't think they will be able to hide it very well."
Parliamentary elections in Russia are set for September 18 to 20.
As fighting rages around the strategic city of Kostiantynivka, Zelenskiy said Russia was losing a "maximum" amount of troops in its bid to advance into Ukraine's so-called fortress belt of eastern cities.
He also hailed recent gains by Kyiv's troops in southeastern Ukraine, adding the amount of territory occupied by Russia and liberated by Ukrainian forces in 2026 would be equal.
Russia is bolstering its battlefield offensive with an escalating air war on Ukrainian cities made worse by a critical shortage of US-designed Patriot interceptors.
Zelenskiy said the 264 interceptors Ukraine is expecting to have received in 2026 represent a significant drop from 2025, when Ukraine received 364, and 2023, when it received 675.
He said Russia was aiming to develop a capacity to produce up to 1300 ballistic missiles per year.
Over the northern summer, Ukraine has escalated a campaign of drone strikes targeting Russian economic infrastructure, including oil refineries and online retailers' warehouses, seeking to destroy infrastructure it says is central to Russia's war effort.
Russian President Vladimir Putin said in comments on Saturday that Kyiv had opened "Pandora's box" by striking economic targets, saying Russia would hit back at Ukraine's "most sensitive economic sectors".
Zelenskiy said Ukraine was facing another difficult winter of Russian strikes on its energy grid, a prospect that had prompted Kyiv's air force to ask for 360 missile interceptors for the season.
He also said he had reached an agreement with France on at least one SAMP/T air-defence system this year, and with Germany on the supply of about 600 PAC-2 and PAC-3 interceptors through 2028.
Ukraine's war effort was further complicated by a $US27 billion ($A38 billion) defence funding gap this year, Zelenskiy said, a result of higher-than-expected spending in the first half of the year.
At least $US8 billion is needed for "a normal start" to 2027, plus about $US20 billion more for military salaries, payments to families of the dead, as well as other financing, he added.
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