(Bloomberg) -- President Joe Biden said US assistance to Ukraine would continue after an explosion at a major dam in the south of the country flooded villages and threatened supplies of drinking water and electricity.

“We’re not leaving,” Biden said during a Cabinet meeting at the White House. “We’re going to help Ukraine.”

Earlier Tuesday, the White House said they were still evaluating what assistance Ukraine may need after the explosion, as well as culpability for the attack. White House National Security Council spokesman John Kirby said the US had not determined whether Russia was responsible, but said it was certain the incident would lead to loss of life and wreak significant havoc in the region. 

Read more: Dam Destroyed in the Dead of Night Upstages Ukraine’s Offensive

“What is clear, and what we absolutely can say, is that the damage to the Ukrainian people and to the region will be significant,” Kirby said. “We know there are casualties including likely many deaths.”

Ukrainian President Volodymyr Zelenskiy blamed Russia for the breach at the Kakhovka hydroelectric plant, which supplies water to Russian-annexed Crimea and feeds cooling systems for the Zaporizhzhia nuclear power plant, one of the biggest in Europe. The Kremlin has denied responsibility.

“We’ve seen the reports that Russia was responsible for the explosion at the dam, which I would remind, Russian forces took over illegally last year, and have been occupying since then,” Kirby said. “We’re doing the best we can to assess those reports.”

Ukraine said the breach unleashed an environmental catastrophe, with floodwater sweeping across the south of the country as Kyiv’s forces intensify their counteroffensive to oust Moscow’s troops from occupied territory.

Kirby said it was too soon to tell what recovery assistance would cost, or if it would alter the administration’s timeline for returning to Congress to request additional assistance. It was also too soon to know what the impact might be on Ukraine’s plans for a summertime counteroffensive, Kirby said.

On Capitol Hill, House Speaker Kevin McCarthy said he opposed a push by fellow Republican hawks seeking additional Ukraine funds to bypass limits on defense spending imposed by the debt-limit deal passed last week. 

McCarthy said he supports Ukraine’s effort to repel Russia’s invasion but would not allow a House vote on legislation he considers an end-run around spending limits. The speaker is seeking to appease conservatives angered by the debt-limit deal with Biden.

Read more: McCarthy Opposes Expedited Ukraine Funding Pushed by GOP Hawks

--With assistance from Jenny Leonard.

(Updates with details on Congress starting ninth paragraph)

©2023 Bloomberg L.P.