End of military agreement leaves US and Russia without limits on nuclear warheads

The end of the New START treaty left the United States and Russia without formal limits on the production, deployment and number of nuclear warheads ready for use, after the agreement expired on Wednesday (4). International security experts say that the absence of the treaty tends to accelerate the nuclear arms race and increase uncertainty on the global stage.

Signed in 2010 by Washington and Moscow, New START limited the number of strategic nuclear warheads ready for use by each country to up to 1,550, in addition to imposing ceilings on launch means and providing for verification mechanisms, in-person inspections and periodic exchange of information. It was the last agreement of its kind in force between the world’s two largest nuclear powers.

With the expiration of the treaty, the US and Russia begin to operate without verifiable restrictions, which, according to analysts, consolidates the end of the arms control logic that marked the post-Cold War period. For professor of International Relations at UFF and Harvard researcher Vitelio Brustolin, New START functioned as a minimum mechanism of predictability between the two countries. “The end of New START removes the last institutional brake that still contained this arms race,” he stated.

Without the agreement, experts estimate that countries tend to plan their arsenals based on the worst possible scenario, which increases the risk of accelerated expansion of warheads and launch systems. Although the Nuclear Non-Proliferation Treaty (NPT) remains in force, analysts point out that it has been insufficient to contain the advance of arsenals, especially in the face of Chinese nuclear expansion.

China is pointed out as one of the main factors behind the emptying of New START. According to estimates by the Stockholm International Peace Research Institute (Sipri), the country has been producing around 100 new warheads per year since 2023 and had at least 600 warheads in January 2025. Experts say that Washington has started to prioritize containing Beijing, while Russia is no longer the sole focus of American nuclear strategy.

US President Donald Trump advocates that any new arms control agreement include China. Beijing, in turn, argues that it should not join such treaties while the US and Russia maintain much superior arsenals. The impasse, according to professor Gunther Rudzit, from ESPM, marks the entry into a “third nuclear era”, characterized by open competition between multiple powers and the absence of strategic trust.

Sipri data indicates that, in January 2025, Russia had at least 5,429 nuclear warheads, while the United States had around 5,177. Both stated, throughout the treaty, that they would respect the limit of 1,550 strategic warheads ready for use. The American State Department recognized, in official documents, that New START strengthened national security by allowing monitoring of the Russian arsenal. Moscow, in turn, regretted the end of the agreement, but declared itself prepared for an unrestricted scenario.

Analysts estimate that the effects of the end of the treaty will not be limited to the USA, Russia and China. Countries that do not have nuclear weapons, such as Germany, Poland, Ukraine, Japan and South Korea, have already shown signs that they may reconsider their policies in the face of the new environment of insecurity. The risk, according to experts, is the spread of atomic arsenals and the increased likelihood of major conflicts.

Furthermore, the modernization of weapons, the development of hypersonic missiles and the increasing use of artificial intelligence in military systems are highlighted as factors that increase the risk of automatic decisions in crisis scenarios. For analysts, the combination of more weapons, fewer rules and greater technological speed makes the global nuclear scenario more unstable than at any time since the end of the Cold War.