"It was a good conversation, but not a conversation that will lead to immediate Peace," President Trump posted on social media.

President Trump said he discussed Ukraine's recent attacks on Russian bombers with Putin, adding that he's not optimistic about "immediate peace."

The Ukrainian operation was “grounds for a nuclear attack,” declared Vladmir Solovyov, a firebrand host on Russian state TV, calling for strikes on the Ukrainian presidential office in Kyiv, and beyond.

Officials from Russia and Ukraine in Istanbul on Monday failed to reach a ceasefire but agreed to exchange more prisoners.

The strikes help Kyiv "negotiate from a position of strength," Oleksandr Merezhko, the head of Ukraine's parliamentary foreign affairs committee, told Newsweek.

Russian forces have continued to advance in the northern Ukrainian region of Sumy, bringing the region’s capital within range of their drones and artillery, according to Ukrainian officials and analysts.