Explosions were also heard as far west as the city of Ivano-Frankvivsk."Christmas should be a time of peace, yet Ukraine was brutally attacked on Christmas Day. Launching large-scale missile and drone attacks on the day of the Lord’s birth is wrong," Kellogg wrote on Dec. 25 on X, formerly known as Twitter."The world is closely watching actions on both sides. The U.S. is more resolved than ever to bring peace to the region."Kellogg, 80, previously held key roles as executive secretary and chief of staff of the U.S. National Security Council under President Trump, and served as a senior advisor to then-Vice President Mike Pence.Ukraine and the U.S. have agreed on a date for Kellogg's first visit to Kyiv in his capacity as peace envoy.