The world's nine nuclear-armed states continue to modernize their nuclear weapons , states the Stockholm International Peace Research Institute (SIPRI).
The Swedish think tank's report notes that countries have deepened their reliance on such deterrence in 2023.
"We have not seen nuclear weapons play such an important role in international relations since the Cold War," said Wilfred Wan, director of SIPRI's Weapons of Mass Destruction Program.
Earlier this month, Russia and its ally Belarus began the second phase of exercises designed to train troops to handle tactical nuclear weapons - part of the Kremlin's efforts to discourage the West from increasing its support for Ukraine.
In a separate report, the International Campaign to Abolish Nuclear Weapons (ICAN) said the nine nuclear-weapon states spent a total of $91.4 billion on their arsenals in 2023 - the equivalent of $2,898 per second. The Geneva-based Coalition of Disarmament Activists won the 2017 Nobel Peace Prize.
The group said the figures show a $10.7 billion increase in global spending on nuclear weapons in 2023 compared to 2022, with the United States accounting for 80 percent of that increase. The US share of the total cost, $51.5 billion, is more than all the other nuclear-weapon states combined.
"There has been a significant upward trend in the amount of funding devoted to the development of these most inhumane and destructive weapons over the past five years," reported Alicia Sanders-Zacre, Policy and Research Coordinator at ICAN.
The next largest spender was China at $11.8 billion, with Russia spending the third largest at $8.3 billion.
"All these means do not improve global security, but actually endanger people wherever they live,", Sanders-Zackre emphasized.
SIPRI estimated that about 2,100 of the deployed warheads were maintained on high operational readiness for ballistic missiles, and almost all belonged to Russia or the United States. However, it is specified that for the first time, China also has some warheads in a state of high operational readiness.
"Unfortunately, we continue to see an annual increase in the number of operational nuclear warheads," said Dan Smith, director of SIPRI. He added that the trend is likely to accelerate in the coming years "and is extremely worrying".
Russia and the United States together possess almost 90% of all nuclear weapons. The size of their military stockpiles remained relatively stable in 2023, although Russia is estimated to have deployed about 36 more operational warheads than in January 2023, SIPRI noted.
SIPRI's 2024 annual report states that transparency regarding nuclear forces has declined in both countries since Russia's invasion of Ukraine in February 2022, and debates over nuclear weapons-sharing agreements have increased in importance.
Washington ended the bilateral strategic stability dialogue with Russia, and last year Moscow announced it was suspending its participation in the New START nuclear treaty.
Of the total global inventory of approximately 12,121 warheads in January, about 9,585 were in military stockpiles for potential use. Approximately 3,904 of these warheads were deployed by missiles and aircraft - up 60 from January 2023 - and the rest were in central storage.
In Asia, India, Pakistan and North Korea are pursuing capabilities to deploy multiple warheads on ballistic missiles, SIPRI noted. The United States, Russia, France, Britain, and China all have this capability, allowing for a rapid potential increase in deployed warheads, as well as the ability for nuclear states to threaten to destroy significantly more targets. The ninth nuclear country is Israel.