Fears grow of new nuclear arms race as key U.S.-Russia treaty expires

Now the world has reverted to an early Cold War mentality, when uncertainty and acceptance of conflict were high, Sokov added.

“It took the Cuban Missile Crisis for everyone to get scared,” he said, referring to when in the early 1960s the U.S. deployed nuclear warheads in the U.K., Italy and Turkey as the Soviet Union sent nuclear missiles to Cuba.

The episode, considered the closest the world came to fullscale nuclear war during the Cold War, ushered in an era of regulation. But global interest in arms control waned in recent decades, Sokov said, as has the fear of a nuclear apocalypse.

That makes the loss of New START significant as a tool that ensured some degree of predictability and communication, he said.

In addition to warhead limits, the treaty provided for data sharing, mutual compliance checks and a mechanism for dialogue to raise and resolve potential misperceptions about what the other side is doing.

Before Moscow suspended New START in 2023, both parties carried out 328 on-site inspections and exchanged more than 25,000 notifications about each other’s activities, according to the State Department.

The two sides can still use satellite imagery, human intelligence and other forms of restricted data to get an idea of where the other side’s nuclear arsenal is in terms of numbers and capabilities, Fabian Rene Hoffmann, a research fellow at the Oslo Nuclear Project at the University of Oslo, said.

“But lack of transparency of course matters, especially in the current low-trust environment,” Hoffmann said.

The expiration means Russia and the U.S. no longer have a mechanism to verify each other’s intentions, according to Dmitry Medvedev, who served as Russia’s president when the treaty was signed in 2010 under President Barack Obama.

Moscow said Wednesday it has still not received an official response from Washington to Putin’s offer, accusing it of an “erroneous and regrettable” approach, but said it was still open for dialogue. China said Thursday it “regretted” the treaty expiring.

Obama also bemoaned the end of the treaty.

“It would pointlessly wipe out decades of diplomacy, and could spark another arms race that makes the world less safe,” he said in a post on X.

The Trump administration said the door was open to talks with both Russia and China.

“President Trump has spoken repeatedly of addressing the threat nuclear weapons pose to the world and indicated that he would like to keep limits on nuclear weapons and involve China in arms control talks,” a Trump administration official told NBC News Monday when asked about the treaty’s expiration.

‘Neither fair nor reasonable’

Trump has said that he wants to pursue a policy of “denuclearisation” with both Russia and China. In response, Beijing has said it is “neither fair nor reasonable” to ask the country to join nuclear disarmament negotiations when its nuclear arsenal is dwarfed by the U.S. and Russia.

The 2025 annual Pentagon report to Congress found that Beijing was on track to have more than 1,000 warheads by 2030 as part of what it called China’s “massive nuclear expansion.”

China’s nuclear build-up is an example of what happens when you don’t have predictability or checks, according to Sokov.

“We know that China is building up, but we don’t know by how much. We don’t know where it’s going to stop,” he said.

A new agreement to replace New START could happen without China, Albertson said, but it should give flexibility to both the U.S. and Russia to be able to respond adequately to Beijing’s nuclear buildup.