During Joe Biden's European trip, the U.S. president labeled his Russian counterpart Vladimir Putin as a "butcher" and said he should not be in power. How do these comments affect the future of the Russia-Ukraine conflict? CGTN talked to Victor Gao, chair professor at Soochow University and chairman of the China Energy Security Institute. Professor Gao said that mankind has never been as close to the brink of nuclear war as we are today. President Biden needs to de-escalate rather than escalate the situation.