Hours before Vance and Zelenskyy were set to meet, a Russian drone with a high-explosive warhead hit the protective confinement shell of the Chernobyl Nuclear Power Plant in the Kyiv region, the Ukrainian president said. Radiation levels have not increased, Zelenskyy and the U.N. atomic agency said.

Trump said on Wednesday he had held a "highly productive phone call" with Putin and they had agreed to start negotiations immediately.

Asked whether Ukraine would be part of the negotiations, the president said on Thursday, “Of course they would.” A day earlier, he had suggested otherwise, and appeared ready to make concessions that Ukraine has flatly rejected.