"The prospect of nuclear conflict, once unthinkable, is now back within the realm of possibility," he said. "It is time to stop the horror unleashed on the people of Ukraine and get on the path of diplomacy and peace."
Guterres called for the safeguarding of nuclear facilities in Ukraine and also announced the U.N. is allocating $40 million from its Central Emergency Response fund to assist Ukrainians, Reuters reported.
"This funding will help get critical supplies of food, water, medicines and other lifesaving aid into the country as well as provide cash assistance," Guterres said.
Russian forces launched a full-blown military invasion of Ukraine nearly three weeks ago on Feb. 24. Four days later, Putin raised the alert status for his nuclear forces to "special regime of combat duty."
President Biden’s national security adviser, Jake Sullivan, said Sunday that despite the apparent threat, Washington’s nuclear alert levels remained unchanged.
"The United States has not adjusted our nuclear posture, but it is something that we monitor day by day, hour by hour because it is a paramount priority to the president," he said.