For the first time in decades, the world’s two largest nuclear superpowers are no longer bound by any treaty limiting their arsenals. The last remaining nuclear arms control agreement between the U.S. And Russia, known as New START, expired Thursday, .
The lapse removes limits on how many nuclear weapons Washington and Moscow could deploy on missiles, bombers and submarines, and ends the requirement that both sides notify one another whenever nuclear weapons were moved. The expiration has raised fears of a new arms race, with both nations now free to build up their nuclear stockpiles without constraint.
Globally, there are more than 12,200 nuclear weapons spread across nine nuclear-armed nations, according to recent analysis. The United States and Russia alone account for roughly 10,636 of those weapons.
The New START treaty, signed in 2010, capped each party at 1,550 deployed nuclear warheads, 700 deployed intercontinental ballistic missiles, submarine-launched ballistic missiles and heavy bombers equipped to transport nuclear weapons, and 800 “deployed and non-deployed” launchers. It also established transparency measures, including data transfers, notifications, and on-site inspections.
UN Secretary-General António Guterres has called the treaty’s end “a grave moment for international peace and security,” urging Russia and the U.S. To negotiate a successor framework “without delay.” He warned that without the treaty, “we face a world without any binding limits on the strategic nuclear arsenals” of the countries possessing the “overwhelming majority of the global stockpile of nuclear weapons.” Guterres stated the risk of nuclear weapon use is the highest it has been in decades.
Pope Leo also urged the two states to renew the treaty, saying the current world situation required “calls for doing everything possible to avert a new arms race.”
U.S. President Donald Trump indicated the United States would not continue to adhere to the limits of the New START Treaty. In a post on Truth Social, Trump stated that rather than extend the treaty – which he described as “a badly negotiated deal” and “grossly violated” – his administration would have “Nuclear Experts work on a new, improved, and modernized Treaty that can last long into the future.”
Some experts argue the limitations of the New START treaty were outdated and unnecessarily constrained the U.S., particularly as China rapidly expands its nuclear arsenal. A 2022 Pentagon report estimated that China could have some 1,500 nuclear warheads by 2035 if it continues to expand its stockpile at the current pace.
Thomas Countryman, a former acting undersecretary of state for arms control and international security, warned that the worst-case scenario is a spiraling escalation that could lead to nuclear conflict.
