The US Under Secretary of State for Arms Control and International Security, Thomas DiNanno, told delegates at the Disarmament Conference in Geneva that extending new START — which set limits on the world's two biggest nuclear powers the United States and Russia — would not benefit the US or the world, as it was flawed and did not include China."Today, the United States faces threats from multiple nuclear powers. In short, a bilateral reaty with only one nuclear power is simply inappropriate in 2026 and going forward," said DiNanno.
Earlier DiNanno told reporters that President Donald Trump has been clear that he wants a new treaty on nuclear arms controls.
The last major nuclear arms control treaty between Russia and the United States expires Thursday, ushering in an era without caps set by the world’s largest nuclear powers.
Without the New START treaty, which caps the number of deployed nuclear warheads at 1,550 on each side, there will be no limits on the American and Russian arsenals. Not only are there no discussions between Washington and Moscow on what comes next, but also officials from both countries are left guessing about the other side’s capabilities and intentions, increasing the possibility of misunderstandings and an unrestricted nuclear arms race not seen since the 1960s, experts and officials warn.
“For the first time in more than half a century, we face a world without any binding limits on the strategic nuclear arsenals” of Russia and the U.S., United Nations Secretary-General António Guterres said in a statement, calling it a “grave moment” for international peace and security.
President Donald Trump referred to the treaty Thursday on Truth Social as a “badly negotiated deal” and said that rather than extend it, “we should have our Nuclear Experts work on a new, improved, and modernized Treaty.”
The U.S. and Russia possess nearly 90% of all nuclear weapons, or more than 10,500 warheads combined, according to the Stockholm International Peace Research Institute’s 2025 assessment. China’s nuclear arsenal currently stands at 600 warheads, but is growing faster than any other country’s, by about 100 new warheads a year since 2023, the report said. Together, the three powers’ nuclear arsenals would wipe out life on Earth several times over.
“The Cold War is full of examples where each side had preconceptions and assumptions about what the other side was doing, some of which was faulty and which led to expensive competitions on who was seen to be ahead or behind,” said Mike Albertson, who was involved in negotiating, ratifying and implementing New START.
The treaty’s demise represents the end of a process of bilateral strategic arms control dating back to the 1960s, “where we and the Soviets and then Russians worked together first to limit and then reduce our nuclear arsenals,” said Albertson.
Russia suspended the treaty in early 2023 over Washington’s support for Ukraine. At the time, Moscow said it would still observe agreed upon restrictions. Since the invasion of its neighbor and amid the U.S.-led negotiations to end the war in Ukraine, the Kremlin has exploited the nuclear threat as a military tactic.
In September, Russian President Vladimir Putin offered to voluntarily continue to abide by the treaty’s limits for another year. Trump said in October the offer was a “good idea” but there has been no official response from Washington.
“If it expires, it expires. We’ll do a better agreement,” Trump said in an interview Jan. 8, arguing that China, which has been building up its nuclear weapons, should be a participant. Beijing has shown no interest in nuclear disarmament talks.
For former Soviet and Russian negotiator Nikolai Sokov, who spent nearly 45 years of his life working on nuclear arms control, the lapsed treaty feels like a personal loss.
“Everything I did in my life is now gone,” he said.
A Yars intercontinental ballistic missile is test-fired from the Plesetsk launch facility in northwestern Russia.Russian Defense Ministry Press Service / via AP
Now the world has reverted to an early Cold War mentality, when uncertainty and acceptance of conflict were high, added Sokov, who is now a senior fellow at the Vienna Center for Disarmament and Non-Proliferation.
“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 United Kingdom, Italy and Turkey as the then-Soviet Union sent nuclear missiles to Cuba.
The episode, considered the closest the world came to full-scale 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, said Fabian Rene Hoffmann, a research fellow at the Oslo Nuclear Project at the University of Oslo.
“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 then=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.
“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.
Trump has said that he wants to pursue a policy of “denuclearization” 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.