"If there is no US support, it means that we have no air defence, no Patriot missiles, no jammers for electronic warfare, no 155-millimetre artillery rounds," he told the Washington Post in an interview published on Friday.

"It means we will go back, retreat, step by step, in small steps," he said. "We are trying to find some way not to retreat."

Shortages of munitions, he said, meant "you have to do with less. How? Of course, to go back. Make the front line shorter. If it breaks, the Russians could go to the big cities."

Zelenskiy's published statements came as officials said massive Russian missile and drone attacks hit thermal and hydro power plants in central and western Ukraine overnight.

Democratic President Joe Biden has urged the Republican-controlled US House of Representatives to endorse the military and financial aid package, but House Speaker Mike Johnson has held up the matter for months, citing domestic priorities.

Zelenskiy told Johnson in a telephone conversation on Thursday that approval of the package was vital.

Russian forces captured the eastern town of Avdiivka last month and have made small gains since, but the front lines have changed little in months.

Ukrainian troops have been unable to advance, and Zelenskiy said Kyiv intended to pursue attacks on targets in Russia, including oil refineries.

He said Washington's reaction to the wave of Ukrainian attacks was "not positive", but Kyiv was using its own drones.

"We used our drones. Nobody can say to us you can't," he told the newspaper. "If there is no air defence to protect our energy system and Russians attack it, my question is: Why can't we answer them?" he said.

"Their society has to learn to live without petrol, without diesel, without electricity. When Russia will stop these steps, we will stop."

In the latest barrage targeting Ukraine's already damaged power infrastructure, Kaniv hydropower plant was among the targets along with Dnister plant.

"The terrorist state of Russia wishes to repeat the ecological disaster in the Kherson region following Russia's destruction of the Kakhovka HPP (blown up by Russian forces last year). This time, not only Ukraine but also Moldova are at risk," Zelenskiy said on X, formerly Twitter.

Last week, Russia also hit Ukraine's largest dam, the DniproHES in the southern Zaporizhzhia region, eight times during a massive overnight attack.

A senior official at the Centrenergo generating company reported that the 10-unit Zmiivska thermal plant in northeastern Kharkiv region, an area subject to many Russian attacks, had been destroyed in a big wave of strikes on March 22.

"There were many direct hits. Everything we repaired in preparation for the winter was destroyed," Andriy Hota, chairman of the company's supervisory board told Interfax Ukraine news agency.

The wave of attacks on March 22 was described by Kyiv officials as the most intense since the February 2022 invasion.

Prime Minister Denys Shmyhal said energy facilities in a total of six regions had been damaged.

Power grid operator Ukrenergo said on Telegram it had to apply power-cut schedules up till the evening in three regions - Dnipropetrovsk, Zaporizhzhia and Kirovohrad.

The largest private power firm, DTEK, said its three thermal power plants had come under attack on Friday, and equipment was severely damaged.

It added that Russian strikes on energy facilities were becoming more "accurate and concentrated".

The Ukrainian military said its air force had destroyed 58 Russia-launched attack drones overnight from a total of 60, along with 26 of 39 missiles of various types.

Australian Associated Press