Guterres said rising global tensions have driven military spending to unprecedented levels and made conflicts more dangerous.
In a statement released Thursday, he said the spread of small arms and light weapons, along with emerging technologies, is increasing the lethality of wars.
The UN chief warned that world leaders must act to prevent further escalation and stop threatening the use of nuclear weapons.
He also urged governments to halt arms races and invest in strengthening peace and trust among nations instead of expanding military arsenals.
Guterres stressed that fulfilling disarmament commitments and strengthening non-proliferation systems could help prevent major catastrophes and build a safer world.
Tensions have sharply escalated in recent weeks following military exchanges involving Iran, Israel and the United States, with missile strikes, drone attacks and air operations reported across parts of the Middle East.
