The scheduled expiry of the New START nuclear arms treaty between the United States and Russia on Thursday marks the end of a major era of bilateral disarmament agreements and reflects a changing nuclear landscape shaped by China’s rising influence and new military technologies.
What does New START cover?
Signed in 2010, the accord was a key component of the U.S. administration's policy to reset relations with the Kremlin.
New START limited the arsenals of the two nuclear powers to a maximum of 1,550 deployed strategic offensive warheads each, a reduction of nearly 30 percent compared with the previous ceiling set in 2002.
It capped the number of launchers and heavy bombers at 800.
Crucially, the treaty also provided for mutual inspections of military sites, a pillar of the "trust but verify" disarmament policy when Ronald Reagan was U.S. president.
Moscow and former U.S. president Joe Biden's administration reached a last-minute deal in January 2021 to extend it until Feb. 4, 2026, in a climate of mistrust that predated Russia's invasion of Ukraine on Feb. 24, 2022.
Mutual inspections abandoned
On Aug. 9, 2022, Russia announced it was suspending U.S. inspections of its military sites under the treaty, saying this was in response to U.S. obstacles to Russian inspections in the United States.
No inspections have taken place since, reducing New START to a commitment to remain under the agreed limits.
In September 2025, Russian President Vladimir Putin proposed extending the treaty's terms for one year, an idea U.S. President Donald Trump approved but has not followed up on.
"This proposal concerned only the caps to the numbers of warheads, which is not the most important element when talking about arms control," said Heloise Fayet of the French Institute of International Relations (IFRI).
"The most important part of New START, inspections and mutual verification, is not included."
The treaty's expiry raised fears of a renewed arms race, which Pope Leo XIV on Wednesday urged the world to avert.
The Kremlin said it would act "responsibly" after the expiration.
Technical constraints are expected to limit how quickly both sides could increase their arsenals, however.
"The bottlenecks are hard to assess on the Russian side," Fayet said.
"For the Americans, they can reactivate warheads held in storage, which is not very complicated, especially as the U.S. National Nuclear Security Administration is stepping up its production of tritium, a crucial gas."
On Jan. 26, the NNSA said it had completed a record 13 tritium extractions in nine months.
"The successful delivery of tritium is essential to meeting the Department of War's deterrent requirements," said NNSA Administrator Brandon Williams.
"This accomplishment significantly strengthens our national security and reinforces the strategic readiness of our deterrent mission."
New nuclear order
China's growing nuclear capabilities and technological advances such as AI, deep-strike weapons and space-based systems are reshaping the nuclear landscape and questioning the treaty's relevance.
China, the world's third-biggest nuclear power, is still far behind Russia and the United States but developing its capabilities at a rate that concerns Washington.
Some analysts warn that the United States risks facing having to maintain deterrence on two fronts, a challenge observers have called "the two nuclear peer problem".
It could have to defend against Moscow and Beijing, and be potentially constrained if bound by a treaty only with Russia.
Beijing has so far refused to enter negotiations on a treaty.
Technological revolutions are also "creating new ways to deter and constrain an adversary", complicating strategic calculations, Fayet noted.
For example, the U.S. Golden Dome project, which envisages missile-interception capabilities based in space, worries Moscow because it could challenge the principle of mutual vulnerability, a cornerstone of deterrence dialogue.
In this context, Fayet said, "the expiry of New START can be seen as an opportunity to pursue arms control differently."
This, she suggested, could be done "by including new technologies in the framework, by regulating types of delivery systems rather than simply counting warheads, or for example by agreeing not to include AI in nuclear weapons".