Ukraine’s President Volodymyr Zelensky raised the stakes ahead of a potential meeting with Vladimir Putin in Turkey by saying he wouldn’t hold talks with any Russian representative other than the president himself.

After Mr. Trump expressed frustration with Russia’s refusal to stop the war, Mr. Putin ordered a three-day cease-fire to begin on May 8, in order to mark the May 9 celebration of the Soviet Union’s victory over Nazi Germany in World War II. Mr. Zelensky described that pledge as a “ manipulation .”