World enters uncharted era as US-Russia nuclear treaty expires, opening door to fastest arms race in decades

A historic nuclear arms reduction treaty is set to expire Thursday, which will thrust the world into a nuclear situation it has not faced in more than five decades, one in which there are no longer any binding limits on the size of Russia’s or America’s nuclear arsenals and no inspection regime to verify what Moscow does next.

Matt Korda, associate director of the Nuclear Information Project at the Federation of American Scientists, said the expiration of the New START treaty forces both countries to rethink assumptions that have guided nuclear planning for more than a decade. 

“Up until now, both countries have planned their respective nuclear modernization programs based on the assumption that the other country is not going to exceed those central limits,” Korda said. “Without those central limits … both countries are going to be reassessing their programs to accommodate a more uncertain nuclear future.”

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Russia had already suspended its participation in New START in 2023, freezing inspections and data exchanges, but the treaty’s expiration eliminates the last legal framework governing the size of the two countries’ nuclear arsenals.

With no follow-up agreement in place, the administration has insisted it cannot agree to arms control without the cooperation of China. 

“The president has been clear in the past that in order to have true arms control in the 21st century, it’s impossible to do something that doesn’t include China because of their vast and rapidly growing stockpile,” Secretary of State Marco Rubio said Wednesday.

Experts are skeptical that China would ever agree to limit its nuclear stockpile until it’s reached parity with the U.S., and Russia has said it would not pressure China to come to the table. 

China aims to have 1,000 nuclear warheads by 2030, but even that figure pales in comparison to the aging giants of the Cold War. As of early 2026, the global nuclear hierarchy remains top-heavy, with the U.S. and Russia holding roughly 86% of the world’s total inventory. Both the U.S. and Russia hold around 4,000 total warheads, with close to 1,700 deployed by each. Global nuclear stockpiles declined to about 12,000 in 2025, down from more than 70,000 in 1986.

In February 2023, Russia announced it was suspending its participation in the New START treaty, halting inspections and data-sharing under the pact while saying it would continue to respect the numerical limits. But, more recently, it floated the idea of extending the treaty by another year.

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Korda said that proposal reflected shared constraints rather than a sudden change in Russian intentions. 

“It’s not in Russia’s interest to dramatically accelerate an arms race while its current modernization programs are going so poorly and while its industrial capacity is tied up in Ukraine,” he said.

Korda said that without inspections and data exchanges, countries are forced to rely on their own intelligence, increasing uncertainty and encouraging worst-case planning. 

“Without those onsite inspections, without data exchanges, without anything like that, all countries are really left with national technical means of being able to monitor each other’s nuclear forces,” Korda said.

With New START’s limits gone, experts said the immediate concern is not the construction of new nuclear weapons but how quickly existing warheads could be deployed. Ankit Panda, a Stanton senior fellow at the Carnegie Endowment for International Peace, said Russia could move faster than the United States in the near term by “uploading” additional warheads onto missiles already in service. 

“Uploading would be a process of adding additional warheads to our ICBMs and submarine-launched missiles,” Panda said. “The Russians could be much faster than the United States.”

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Korda said a large-scale upload would not happen overnight but could still alter force levels within a relatively short window. 

“We’re looking at maybe a timeline of about two years and pretty significant sums of money for each country to execute a complete upload across the entire force,” he said, adding that, in a worst-case scenario, it could “roughly result in doubling the sizes of their deployed nuclear arsenals.”

That advantage, however, is constrained by longer-term industrial realities. Panda noted that the U.S. nuclear weapons complex lacks the production capacity it once had, limiting how quickly Washington could sustain a larger arsenal over time. 

“The United States is currently unable to produce what is going to be a target for 30 plutonium pits,” a fraction of Cold War output, he said.

Nicole Grajewski, a fellow at the Carnegie Endowment for International Peace, said Russia’s ability to produce nuclear weapons may be faster than the U.S. in some, but not all, parts of the development chain. 

“Russia is very good at warhead production,” she told Fox News Digital. “What Russia is really fundamentally constrained on is the delivery vehicle side of it.”

Grajewski added that this is particularly true as the war in Ukraine continues. Russia’s production of missiles and other delivery systems relies on facilities that also support conventional weapons used in the war, limiting how quickly Moscow could expand the intercontinental missiles, submarine-launched weapons and bombers that made up the core of New START.

As a result, Grajewski said she is less concerned about a rapid buildup of those treaty-covered forces than about Moscow’s continued investment in nuclear systems that fall outside traditional arms control frameworks. 

“What is more concerning is Russia’s advances in asymmetric domains,” she said, pointing to systems such as the Poseidon nuclear-powered torpedo and nuclear-powered cruise missiles, which are not covered by existing treaties.

President Donald Trump has previously said he wants to pursue arms control with both Russia and China before suggesting the U.S. should resume nuclear testing.

“If there’s ever a time when we need nuclear weapons like the kind of weapons that we’re building and that Russia has — and that China has, to a lesser extent, but will have — that’s going to be a very sad day,” Trump said in February 2025. “That’s going to be probably oblivion.”

But, in October, he declared, “Because of other countries’ testing programs, I have instructed the Department of War to start testing our Nuclear Weapons on an equal basis. That process will begin immediately.”

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