KYIV, Ukraine >> More civilians died across Ukraine Sunday as analysts warned that delays in U.S. military assistance would see Kyiv struggle to fight off Russian offensives.

One man was Sunday killed after a Russian drone hit the truck he was driving in the Sumy region, the local prosecutor’s office said. Elsewhere, a 67-year-old woman was killed after shelling hit an apartment block in the Donetsk region, said Gov. Vadym Filashkin.

Officials in the Kharkiv region also said Sunday that they had retrieved the bodies of a 61-year-old woman and a 68-year-old man killed by a Russian strike the previous day. Ten Russian Shahed-type drones were shot down over the Kharkiv region overnight, the Ukrainian Air Force said Sunday.

Meanwhile, shelling in the Russian-occupied Kherson region killed two civilians Sunday, said Moscow-installed leader Vladimir Saldo. Ukrainian drones were also reported in Russia’s Krasnodar and Belgorod regions and over the Black Sea, the Russian Defense Ministry said.

The news came as the Institute for the Study of War, a Washington-based think tank, warned that delays in Western military assistance would increasingly hamper Ukraine’s ability to push back Russian advances.

With the war in Ukraine entering its third year and a vital U.S. aid package for Kyiv stuck in Congress, Russia has used its edge in firepower and personnel to step up attacks across eastern Ukraine. It has increasingly used satellite-guided gliding bombs — dropped from planes from a safe distance — to pummel Ukrainian forces beset by a shortage of troops and ammunition.

In its report, the ISW said that Russian forces were prioritizing grinding, tactical gains with operational-level efforts focusing on the cities of Lyman, Chasiv Yar, and Pokrovsk.

“The Russian military command likely assesses that Ukrainian forces will be unable to defend against current and future Russian offensive operations due to delays in or the permanent end of U.S. military assistance,” the think tank said.

Ukraine’s military chief, Gen. Oleksandr Syrskyi, said Saturday that Ukraine’s battlefield situation in the industrial east had “significantly worsened in recent days,” as warming weather allowed Russian forces to launch a fresh push along several stretches of the more than 1,000-kilometer (620-mile) -long front line.

In an update on the Telegram messaging app, Syrskyi said that Russian forces had been “actively attacking” Ukrainian positions near the cities of Lyman, Bakhmut and Pokrovsk, and beginning to launch tank assaults as drier, warmer spring weather made it easier for heavy vehicles to move across previously muddy terrain.