President Volodymyr Zelenskyy has warned that Russia is targeting Ukrainian nuclear substations, in an effort to cut off heat and power while the country suffers its coldest winter since Moscow first invaded in 2014. With temperatures hitting minus 20C, Kyiv’s energy system, weakened by months of Russian aerial attacks, is teetering under the strain of rising winter demand, heavy bombardment and a growing shortage of air defence munitions. “The combination of extreme cold and wave after wave of Russian attacks are pushing Ukraine’s energy system to the edge,” Maxim Timchenko, chief executive of DTEK, Ukraine’s largest private energy company, told the FT. “We are facing an unprecedented threat and fighting for every megawatt.” Ukrainian officials say Moscow’s objective is to weaponise winter, grinding down civilian resolve and forcing Kyiv’s hand at the negotiating table, where the Trump administration is pushing to end the war. A Ukrainian delegation arrived in Miami over the weekend to continue talks with US counterparts.

Ukraine’s US ambassador Olha Stefanishyna said Kyiv and Washington aimed to sign a key document on the country’s economic prosperity in Davos next week. A separate agreement on security guarantees has been more challenging but two senior Ukrainian officials told the FT they hoped to agree on a general “terms sheet” to be signed in Washington shortly after Davos. Russia has particularly targeted the Ukrainian capital, with waves of missiles and drones aimed at electrical and heating infrastructure. Weather forecasts predict at least another 10 days of sub-zero temperatures, as Kyiv is blanketed in thick ice and snow, and the mighty Dnipro river that bisects the city has frozen over. Electricity blackouts have lasted days in some districts of the capital. A week ago, more than 6,000 residential buildings were without heating, according to DTEK. Dozens of apartment blocks remain without heat, say the company and local authorities. “Russia is betting it can break us through energy terror,” Denys Shmyhal, Ukraine’s energy minister, told parliament on Friday. He said there was “not a single power plant left in Ukraine that has not been attacked by the enemy”. Timchenko said his company had deployed “hundreds of teams on the ground doing everything they can to keep energy flowing”. “What is at stake is not only heat and light, but critical services to life like water and sanitation,” he said. Kyiv mayor Vitali Klitschko said on Friday that all schools in the capital would close until February 1 to prioritise “the safety of children . . . in difficult conditions”. He has also urged residents to ride out the cold front elsewhere and leave the capital if they can. Most people, though, are unable to leave. Local authorities have set up tents and “invincibility centres” inside public buildings where people warm themselves, charge their electronic devices and get a hot meal. Ukraine’s state railway company, with the help of several international NGOs, equipped 100 carriages to serve as mobile warming and charging hubs. This week alone, Zelenskyy said on Sunday, Russia launched more than 1,300 attack drones, around 1,050 guided aerial bombs and 29 missiles of various types at Ukrainian critical infrastructure. Overnight, more than 200 drone strikes also targeted the Sumy, Kharkiv, Dnipro, Zaporizhzhia, Khmelnytskyi, and Odesa regions, he said, killing at least two people. Zelenskyy said each strike “undermines” the US and other countries’ efforts to end the war: “Ukraine is being as constructive as possible in diplomacy, while Russia is focused only on strikes and on tormenting people.” He has warned that the country’s air defence munition stocks are running perilously low, saying on Friday that until that morning, several systems had been without missiles.

Ukraine’s military intelligence chief Oleh Ivashchenko warned Zelenskyy on Saturday that Russia was preparing even more targeted strikes on substations that power the country’s nuclear plants. In Kyiv, some people are toughing it out inside their dark and chilly homes, layering themselves in heavy clothing and blankets and huddling around candles. In a viral video posted on Facebook, Valeriy Chaly, a former Ukrainian ambassador to the US, showed how he was using a camping burner to fry eggs at home. Chaly quipped that there were some upsides to the crisis. “Family relationships are warming up” and Ukraine’s “national identity is growing stronger”, he said. “Empathy has increased,” he added. If Ukrainians had grown detached from the harsh realities of life on the frontline for the tens of thousands of troops defending the country, now they have a renewed sense of their sacrifice. “Not everyone knows what it’s like to be in a trench under fire, but what it’s like to live in minus 20°C . . . people understand,” he said.