U.N. Secretary-General Antonio Guterres has warned that impunity, inequality and uncertainty are creating an "unsustainable world."

Guterres told an annual summit of world leaders Tuesday that the situation in war-torn Gaza "is a non-stop nightmare" and condemned the growing "level of impunity" worldwide.

"The level of impunity in the world is politically indefensible and morally intolerable," Guterres said in his speech to the General Assembly, adding that "a growing number of governments and others feel entitled to a 'get out of jail free' card."

"We can't go on like this," he said.

Guterres was speaking as the General Assembly’s annual debate among presidents, prime ministers, monarchs and other leaders that began Tuesday.

Citing deepening geopolitical divisions, wars with no end in sight, climate change and nuclear and emerging weapons, he says humanity is "edging towards the unimaginable – a powder keg that risks engulfing the world."

But, he said, "the challenges we face are solvable" if the international community confronts the uncertainty of unmanaged risks, the inequality that underlies injustices and grievances and the impunity that undermines international law and the U.N.‘s founding principles.