AT A GLANCE
- The New START nuclear arms control treaty between the U.S. and Russia officially expired Thursday.
- The treaty capped deployed nuclear warheads at 1,550 for each country and included inspections and data sharing.
- With no replacement agreement or active negotiations, experts warn of rising mistrust and the risk of a renewed arms race.
- The U.S., Russia, and China now hold arsenals capable of global destruction multiple times over.
Without the New START Treaty, Which Caps Deployed Nuclear Warheads at 1,550 on Each Side, There Will Be No Limits on the U.S. and Russian Arsenals
The expiration of the New START treaty on Thursday has pushed the United States and Russia into uncharted territory, leaving the world’s two largest nuclear powers without any binding limits on their strategic arsenals for the first time in more than half a century.
The treaty had capped deployed nuclear warheads at 1,550 on each side and created a framework for inspections, data sharing, and communication intended to reduce misunderstandings and escalation.
Without New START, there are now no formal restrictions on U.S. or Russian nuclear stockpiles and no active negotiations in place to replace it. Officials and experts warn that the lack of transparency and predictability increases the risk of miscalculation, particularly in an already strained geopolitical environment shaped by the war in Ukraine and deteriorating U.S.-Russia relations. United Nations Secretary-General António Guterres called the treaty’s expiration a “grave moment” for international peace and security, noting that the world has lost one of its last remaining guardrails against nuclear escalation.
The United States and Russia together control nearly 90% of the world’s nuclear weapons, totaling more than 10,500 warheads combined, according to the Stockholm International Peace Research Institute’s 2025 assessment.
China, while still far behind in overall numbers, has the fastest-growing nuclear arsenal, now estimated at about 600 warheads and increasing by roughly 100 per year since 2023. Analysts warn that the combined arsenals of the three countries are more than enough to devastate the planet multiple times over.
Arms control experts say history offers sobering lessons. During the Cold War, false assumptions and worst-case thinking often fueled costly and dangerous arms races. Mike Albertson, who helped negotiate and implement New START and now serves at Lawrence Livermore National Laboratory, said past experience shows how easily mistrust can spiral when there are no agreed limits or verification mechanisms in place.
New START was signed in 2010 by then-President Barack Obama and then-Russian President Dmitry Medvedev, continuing a tradition of bilateral arms control that began in the 1960s. Russia suspended its participation in the treaty in early 2023, citing U.S. support for Ukraine, though it initially said it would continue to observe the limits. Inspections and compliance checks, however, came to a halt.
In September, Russian President Vladimir Putin offered to voluntarily adhere to the treaty’s limits for another year. Then-President Donald Trump said the proposal was a “good idea,” but no formal agreement followed and the treaty expired without renewal. Moscow has since accused Washington of failing to respond, while maintaining that it remains open to dialogue.
Beyond limiting warhead numbers, New START played a critical role in maintaining communication. Before Russia’s suspension, the two countries conducted more than 328 on-site inspections and exchanged over 25,000 notifications related to missile tests, deployments, and other nuclear activities. Those measures provided a level of insight and reassurance that experts say is now missing. While satellite imagery and intelligence gathering can still offer clues, analysts stress that they are no substitute for direct verification in a low-trust environment.
China’s growing nuclear program further complicates the picture. The Trump administration has argued that any future arms control agreement should include Beijing, but Chinese officials have rejected that idea, saying it is unreasonable given the vast disparity between China’s arsenal and those of the U.S. and Russia. A 2025 Pentagon report estimates China could surpass 1,000 warheads by 2030 as part of what it described as a massive nuclear expansion.
For veteran arms negotiator Nikolai Sokov, the loss of New START feels deeply personal after decades spent working on nuclear agreements.
He warned that the world is slipping back toward an early Cold War mentality marked by uncertainty and a higher tolerance for confrontation. Still, he and other experts caution against panic, arguing that the absence of a treaty does not automatically mean an immediate arms race.
The greater danger, they say, lies several years down the road if unchecked competition resumes, not necessarily through sheer numbers of warheads, but through the development of more precise, sophisticated, and harder-to-intercept weapons. Without renewed talks, the predictability that once helped prevent catastrophe has eroded, leaving diplomacy racing against time to reestablish limits before the nuclear balance becomes even more unstable.
