A ceasefire in Russia’s 3-year-old war in Ukraine hinges on Moscow accepting the U.S. proposal of a 30-day pause in fighting as a confidence-building measure for both sides to hammer out a longer-term peace plan.

The barrage comes less than 24 hours after Russian President Vladimir Putin discussed details of the U.S. proposal for a 30-day ceasefire with a U.S. envoy.

Russia and Ukraine continued aerial attacks on each other, inflicting injuries and damages, officials said early on Sunday, as the fate of a proposed ceasefire to the three-year-old war remained uncertain.