Uncertainty has grown in recent days about Moscow's commitment to U.S.-led peace efforts, as Russian officials have raised objections about cornerstones of the nascent proposals.

Russia’s top diplomat said in an interview released on Friday that “there is no meeting planned” between President Vladimir V. Putin of Russia and President Volodymyr Zelensky of Ukraine. It was the Kremlin’s most direct declaration yet that a summit the White House suggested was imminent was nowhere close to materializing.