UN warns nuclear stockpile decline reverses for first time since Cold War

October 2, 2026 at 02:29 AM2 min

This digest was compiled by AI from multiple sources — links to the originals are below.

UN Secretary-General António Guterres warned on September 29 that the world is entering its most dangerous nuclear period since the Cold War. The number of new warheads being added to arsenals now exceeds those being dismantled, reversing decades of decline. The warning came as the New START treaty between the United States and Russia expired on February 5, 2026, leaving no limits on the two largest nuclear arsenals.

Key Facts

UN Secretary-General António Guterres issued the warning at a high-level meeting on the total elimination of nuclear weapons at UN headquarters in New York on September 29.
The New START treaty between the United States and Russia expired on February 5, 2026, leaving no successor agreement in place.
More than 12,000 nuclear warheads exist worldwide, of which 2,100 to 2,200 are on high operational alert and mounted on ballistic missiles.
The UN says the number of new, more advanced warheads being added to arsenals now exceeds the number of older warheads being retired and dismantled.
Guterres called on the United States and Russia to return to negotiations and agree on a replacement for New START.

The Warning

The warning was delivered on September 29 at a high-level meeting on the total elimination of nuclear weapons held at United Nations headquarters in New York. UN Secretary-General António Guterres said the world is passing through its most dangerous nuclear period since the end of the Cold War. The total number of nuclear weapons worldwide declined for many years after the Cold War, but the UN says that trend has now reached a turning point. The number of new and more advanced nuclear warheads being added to national arsenals has begun to exceed the number of older warheads being retired and destroyed.

Treaty Collapse

The New START treaty between the United States and Russia expired on February 5, 2026, and no replacement agreement was reached. For the first time in more than half a century, there is no limit binding the strategic arsenals of the world's two largest nuclear powers. Guterres called on the United States and Russia to return to the negotiating table and agree on a new treaty to replace New START. The UN warns that if a new arms race cannot be prevented, decades of post-Cold War nuclear disarmament progress could be reversed.

Current Arsenal

According to UN data, more than 12,000 nuclear warheads exist worldwide, with 2,100 to 2,200 of them on high operational alert and mounted on ballistic missiles. These weapons can be launched within a very short time, increasing the risk of a wrong decision or miscalculation during a crisis. Many nuclear powers are modernizing their existing weapons and investing in new missiles and other delivery systems. Guterres warned that technological advances, including artificial intelligence and cyber technologies entering military decision-making, are increasing the chance of error and miscalculation.