President Donald Trump, who has recently sharpened his tone against Russia, threatened harsher sanctions earlier this month if a peace deal was not reached within 50 days.

Russia launched a massive attack on Ukraine overnight into Saturday with hundreds of drones, killing at least one person, part of a stepped-up bombing campaign that has dashed hopes for a breakthrough in efforts to end the more than 3-year-old war.

The Kremlin said on Friday that it did not believe that a tougher stance U.S. President Donald Trump has adopted towards Russia over its war in Ukraine means the end of U.S-Russia talks aimed at reviving their battered ties.