US-backed trilateral talks involving Ukraine and Russia will take place next week in Abu Dhabi, President Volodymyr Zelensky said on Sunday, as Ukrainians faced uncertainty over the fate of an energy ceasefire with Russia amid plunging temperatures.

Kyiv is under US pressure to secure peace in the nearly four-year-war while grappling with a Russian campaign of air strikes that has ravaged its energy system during one of the coldest winters in years.

The first round of negotiations took place in late January but led to no new movement on the vital question of territory, with Moscow still demanding Kyiv cede more land in its war-torn east, which it refuses to do.

Zelensky said the new talks would take place on February 4 and 5, and that Ukraine - struggling to stop grinding Russian advances on the battlefield - was ready for a “substantive discussion”.

“Ukraine is ready for a substantive discussion, and we are interested in ensuring that the outcome brings us closer to a real and dignified end to the war,” Zelensky wrote on X.

In the capital Kyiv, 1,000 apartment buildings remained without heating on Sunday, said Mayor Vitali Klitschko, as a new wave of bitter cold swept across much of the country.

Temperatures in the city on Sunday hovered around -15 degrees Celsius, as workers raced to restore heating to hundreds out of the nearly 3,500 high-rises affected by a widespread grid malfunction on Saturday.

Officials did not directly link it to war damage, but the resulting blackouts - which spread to neighbouring Moldova - underlined the vulnerability of Ukraine’s energy system after months of Russian attacks.

The Kremlin said two days ago it had agreed to halt strikes on energy infrastructure until Sunday at the request of US President Donald Trump, and Kyiv said it would reciprocate.

Ukraine said the suspension was supposed to last until the following Friday.

The countries have not reported major strikes on their energy systems in recent days, though Zelensky said on Sunday that Russia was attempting “to destroy logistics and connectivity between cities and communities” through ongoing air attacks.

In southeastern Ukraine, two people were killed overnight in a drone strike on a residential building in the city of Dnipro, and six people were wounded in an attack on a maternity hospital in Zaporizhzhia, regional officials said.

Temperatures are expected to drop even further on Monday to well below minus 20 degrees Celsius in Kyiv.

Ukrainian private energy firm DTEK said on Sunday it had restored power to 300,000 households in the southern coastal region of Odesa, which had been hit hard by the malfunction.

Grid operator Ukrenergo said late on Saturday that planned outages would be in force throughout the entire country.

Anatoliy Veresenko, a 65-year-old veteran who was out for a run at a Kyiv park, said he was warily anticipating new attacks and did not place much hope in the peace process.

“Talks are talks. We hope for peace, but we still need to fight and secure victory.”