The Stockholm International Peace Research Institute says Russia and the US possess ‘almost 90 percent of all nuclear weapons’.

The world’s nine nuclear-armed states have raised their reliance on nuclear weapons, a watchdog has said.

A report released by Stockholm International Peace Research Institute (SIPRI) on Monday said the states increased their spending on modernising their atomic arsenals by one-third last year. The watchdog pointed to the contribution of the wars in Ukraine and Gaza to the deterioration of international security.

Wilfred Wan, director of SIPRI’s weapons of mass destruction programme, said nuclear weapons have not been seen “playing such a prominent role in international relations since the Cold War”.

The report found that the effects of the wars in Ukraine and Gaza are “visible in almost every aspect of the issues connected to armaments, disarmament and international security examined”.

The nine nuclear armed states – the United States, Russia, the United Kingdom, France, China, India, Pakistan, North Korea and Israel – modernised their nuclear arsenals and several “deployed new nuclear-armed or nuclear-capable weapon systems in 2023”, SIPRI found.

The estimated global inventory of 12,121 warheads in January 2024, marked a reduction of 391 compared with the previous year, a year, with about 9,585 in military stockpiles for possible use.

However, about 3,904 of these were deployed were deployed with missiles and aircraft, which is 60 more than in January 2023.

The vast majority of those deployed warheads belong to Russia and the US, although China is believed to have “some warheads on high operational alert” for the first time.

Separately, the International Campaign to Abolish Nuclear Weapons (ICAN) said the combined total spending on nuclear arsenals grew by $10.7bn to $91.4bn in 2023.

The US was responsible for 80 percent of the rise in spending. Its budget of $51.5bn was higher than that of the other eight nuclear-armed countries combined.

The next biggest spender was China at $11.8bn, ICAN said. Russia was third at $8.3bn.

“While the global total of nuclear warheads continues to fall as Cold War-era weapons are gradually dismantled, regrettably, we continue to see year-on-year increases in the number of operational nuclear warheads,” said SIPRI Director Dan Smith.

“This trend seems likely to continue and probably accelerate in the coming years and is extremely concerning.”

The report added that Russia and the US possess “almost 90 percent of all nuclear weapons”. The overall size of their stockpiles has remained “relatively stable in 2023”, it said, although it noted that Russia is estimated to have deployed about 36 more warheads with operational forces than in January 2023.

In its SIPRI Yearbook 2024, the institute said transparency about nuclear forces has declined in both countries due to Russia’s war on Ukraine and debates around nuclear-sharing arrangements.

Washington suspended its bilateral strategic stability dialogue with Russia, and last year, Moscow announced it was leaving the New START nuclear treaty.

SIPRI added that while there were claims that Russia deployed nuclear weapons on Belarusian territory, there was “no conclusive visual evidence that the actual deployment of warheads has taken place”.

The institute stressed that all of its estimates were approximate, and it revises its world nuclear forces data each year based on new information and updates to earlier assessments.