Several Ukrainian officials have warned that the country faces a tough winter but can prevail in the face of Russian missile attacks on its infrastructure.

Maksym Tymchenko, Chief Executive Officer of DTEK, a major power company, said that he was confident that there was no chance “for the Russians to plunge Ukraine into darkness.”

Yet, there was a power generation deficit and issues with electricity transmission, he told the Kyiv Security Forum on Friday.

In the capital, he said, the company was trying to introduce “rolling controlled blackouts: 3-4 hours of electricity supply, followed by 4 hours break. This situation will continue, we hope, until next week only, if there are no further attacks. But we are prepared for further attacks.”

He said all six of DTEK’s power stations had been attacked, some of them several times. As of Friday, he said, the company has managed to bring them all back to the grid.

The problem, though, was with connections and transmission, Tymchenko said.

“Transformers, sub-stations, high-voltage transformers: these are what we’ve been in deficit of, and what we appeal to our international partners for. Some of the equipment is already on the way to Ukraine,” he said.

Mayor Vitaliy Klitschko said that last week that Kyiv faced an almost total blackout. “There was no heat and water supply. And about 4,000 employees of utility companies worked day and night to restore them.”

Ukraine’s Defense Minister, Oleksii Reznikov, told the forum that the months ahead would be difficult.

He added: “The enemy still has significant resources, but there are more and more signs that he needs a pause at any cost.”