In a speech to students at Geneva University, Antonio Guterres presented a new disarmament agenda to face challenges emerging in a world where "Cold War tensions have returned."

"Today, the total elimination of nuclear weapons remains our priority," he said, cautioning that long-championed global "efforts to achieve this goal are in state of severe crisis."

"Our world is going backwards," Guterres said, adding that hard won disarmament agreements reached during and right after the Cold War risked crumbling.

The UN Secretary General pointed out that "global military spending and arms competition are increasing, particularly in the most dangerous parts of the world."

"Governments are pouring resources into updating old weapons systems, developing new ones, and entering into what many see as a new arms race, based on quality rather than quantity," he said.

At the same time, around 15,000 nuclear weapons remained in stockpiles around the world, Guterres said.

"Hundreds are ready to be launched within minutes. We are one mechanical, electronic or human error away from a catastrophe that could eradicate entire cities from the map."

Faced with this bleak picture, Guterres said his new agenda was based on three priorities "disarmament to save humanity, disarmament that saves lives, and disarmament for future generations."

He vowed to increase his efforts to "facilitate dialogue" between countries, urging the United States and Russia in particular to resolve a range of disputes over disarmament issues.

- NKorea, Syria -

His comments came shortly after US President Donald Trump cancelled a widely anticipated nuclear summit next month with North Korean leader Kim Jong Un.

"I am deeply concerned by the cancellation," Guterres said, urging the two sides to "continue their dialogue to find a path to a peaceful and verifiable denuclearisation of the Korean peninsula."

The UN chief also voiced concern about the situation in war-ravaged Syria, and in particular the repeated use of chemical weapons there.

He said his new agenda called for "steps to end and prevent the use of other weapons of mass destruction, especially chemical weapons."

Guterres pointed out that since 2014, a UN fact-finding mission had examined 83 incidents involving the alleged use of chemical weapons in war-ravaged Syria, and had determined so far that such weapons had more than likely been used in 14 cases.

"Each use is a crime under international law. Their widespread use may also constitute a crime against humanity," he warned.

Guterres announced the creation of a "new and impartial mechanism" for identifying those who use chemical weapons in Syria.

In his speech, he also highlighted the growing "malicious use of cyber space".

"Cyberattacks on critical infrastructure could have serious consequences for international relations, peace and security. We could even face the creation of cyberweapons of mass destruction," he cautioned.

"If there is a major outbreak of armed conflict in our world... I am sure that it would be preceded by a massive cyber-attack," he said.