Antonio Gueterres warned the world was facing a threat "not seen since the height of the Cold War" as he stressed humanity was "just one miscalculation away from nuclear annihilation”.
Speaking at the opening of the tenth review conference of the signatories to the Non-Proliferation Treaty, an international treaty that came into force in 1970 to prevent the spread of nuclear weapons, Mr Gueterres cited Russia's war in Ukraine and tensions on the Korean peninsula and in the Middle East.
He said the conference, which was originally due to take place in 2020, but was delayed by the Covid-19 pandemic, was "a chance to strengthen" the treaty and "make it fit for the worrying world around us".
“We have been extraordinarily lucky so far, but luck is not a strategy,” he said. “Nor is it a shield from geopolitical tensions boiling over into nuclear conflict.
"Eliminating nuclear weapons is the only guarantee they will never be used.
"Almost 13,000 nuclear weapons are now being held in arsenals around the world. All this at a time when the risks of proliferation are growing and guardrails to prevent escalation are weakening,"
Mr Gueterres’s words come as US president Joe Biden, who was also speaking at the conference, said the United States was ready to outline a new nuclear arms deal with Russia and called on Moscow to demonstrate its ability to negotiate in good faith.
He said the US was prepared to negotiate a new arms control framework to replace the New START treaty with Russia upon its expiry in 2026.
"Russia should demonstrate that it is ready to resume work on nuclear arms control,” he said, adding that China should also look to work with the US.
"In this moment of uncertainty and upheaval on the global stage, reaffirming our shared commitment to the grounding principles of the global non-proliferation regime has never been more crucial.”
A total of 191 states have joined the treaty, including the five nuclear-weapon states.
Conferences to review the operation of the treaty have been held at five-year intervals since the agreement came into effect in 1970.