U.N. chief says nuclear conflict is 'now back within the realm of possibility'

The United Nations' secretary-general has warned the prospect of a nuclear conflict is now "within the realm of possibility" amid the war in Ukraine.

U.N. Secretary-General António Guterres spoke at a briefing on Monday about Russia's invasion of Ukraine, which he said is only "getting worse." The country is "on fire" and "being decimated before the eyes of the world," and the "impact on civilians is reaching terrifying proportions," he said.

Guterres also raised concerns about Russian President Vladimir Putin placing nuclear forces on high alert. 

"Further escalation of the war, whether by accident or design, threatens all of humanity," he said. "Raising the alert of Russian nuclear forces is a bone-chilling development. The prospect of nuclear conflict, once unthinkable, is now back within the realm of possibility." 

Guterres noted it's crucial to ensure the "security and safety of nuclear facilities" in Ukraine, and he said he has been in contact with a "number of countries," including China, France, and Germany, about "mediation efforts" to end the war.  

"It's time to stop the horror unleashed on the people of Ukraine and get on the path of diplomacy and peace," he said, also warning "whatever the outcome, this war will have no winners, only losers."