The Kremlin is yet to officially comment on the new deadline. But Dmitry Medvedev -- the former Russian president and prime minister now serving as the deputy chairman of the country's Security Council -- framed Trump's challenge as a dangerous escalation.

At least 22 Ukrainians have been killed and another 85 injured in Russian strikes across the country overnight, prompting Ukrainian President Volodymyr Zelensky to call for “very harsh, truly painful” sanctions on Russia.

The attack, which came just hours after President Trump gave the Kremlin a new deadline to work toward ending the war, was part of a wave across the country, the authorities said.