Russia’s army has made “slow and uneven progress” in eastern Ukraine because tanks and armoured vehicles are getting stuck in the mud, senior US defence officials have said.

Heavy rain has wreaked havoc on supply chains since the invasion and left Russian troops on the ground vulnerable to counter-attacks, according to an intelligence update from the Pentagon.

Russian troops have made some progress in the Donbas since withdrawing from the north to focus on the east and south, but Ukraine claims its resistance fighters have managed to inflict “colossal losses” on convoys forced to stick to paved roads or risk the increasingly muddy rural terrain.

“We have serious losses but the Russians’ losses are much, much bigger. They have colossal losses,” said Oleksiy Arestovych, a presidential adviser.

Russia’s casualties since it invaded Ukraine have passed 22,000, with 970 tanks taken out, according to the Ukrainian military. Part of the issue is that troops have been largely forced to stick to single-file formations on paved roads, making them easy pickings for artillery and rocket attacks.

A Pentagon official said: “We would assess that Russian forces are making slow, uneven and, frankly, we would describe it as incremental progress in the Donbas.

“The Russians have not overcome all their logistics and sustainment challenges. As it starts to rain more and there’s more mud, it will force them to be ever more reliant on paved roads and paved highways.

“We would expect that some of their progress will be slowed by mud and by weather conditions.”

Britain’s armed forces minister James Heappey said Vladimir Putin would be unlikely to make significant progress ahead of Russia’s Victory Day holiday next month.

“If they are going to try to achieve something by May 9, they will be forced to remain on roads because the mud does not allow for armoured manoeuvre cross-country,” he said.

“What we will see, therefore, is highly canalised Russian columns that, as we saw north of Kyiv, present the Ukrainians with pretty easy pickings.”

In response to its failings in eastern Ukraine, Russia has stepped up its attacks on targets across the rest of the country, including Kyiv and Odesa.

At least one person died and 10 more were injured in Russian missile attacks on a 25-storey block of flats and a factory in the central Shevchenko district.

The attack came barely an hour after UN secretary-general Antonio Guterres held a press conference with Volodymyr Zelensky, the Ukrainian president, in the country’s capital.

In the south, Moscow used a diesel-powered submarine deployed in the Black Sea to hit Ukrainian military targets with Kalibr cruise missiles, according to its ministry of defence.

The Kremlin has also ordered more strikes on Ukrainian rail infrastructure in the west in an attempt to halt deliveries of Western weapons, Kyiv said.