Beyond New START: What Happens Next in Nuclear Arms Control?

The New Strategic Arms Reduction Treaty (New START) is the last remaining treaty limiting US and Russian nuclear forces. Although there is probably too little time for the two nations to negotiate a replacement before New START expires on 4 February 2026, they could continue to observe its limits – and possibly share data about their deployed forces – after that date. This would allow them to retain the transparency, predictability and restraint codified in New START while they negotiate a new treaty. As an alternative, the US could pause its pursuit of arms control in the face of Russia’s record of noncompliance with past agreements and China’s growing nuclear arsenal. However, even in this challenging environment, arms control discussions can still play an essential role in helping the US, Russia and China manage their nuclear competition and reduce the risk of nuclear war.

The Collapse of Nuclear Arms Control

When New START expires, the US and Russia will face a future without any legally binding restrictions on their nuclear forces. They will lose not only the limits on deployed nuclear warheads, but also the insights provided by the treaty-mandated monitoring and transparency measures. These features have helped the two nations manage their nuclear competition, while avoiding misunderstandings and worst-case assessments, for more than 50 years.

But the international security environment has changed significantly since New START entered into force in 2011. Russia’s noncompliance with past treaties, its invasion of Ukraine and its malign activities across Europe have generated concerns about whether it can be a credible partner in future arms control agreements. China’s growing nuclear force posture, its broader military expansion and its challenges to US allies and partners in the Indo-Pacific have raised questions of whether the US should expand its own nuclear force posture in response or engage with China on arms control.

Competing views about the future of nuclear arms control reflect a fundamental debate about the role that arms control can play in helping to manage great power nuclear competition. For some, bilateral nuclear arms control imposes unwarranted limits on the size and flexibility of the US nuclear force posture. It could, therefore, impede the US ability to respond to China’s growing nuclear arsenal and Russia’s aggressive posture in Europe. Others, however, argue that arms control has brought undeniable benefits to the US, Russia and the international community. The two nations have sharply reduced their nuclear arsenals over the past 50 years and have developed tools they can use to reduce the risks of nuclear war. In this vein, adding China to the process would broaden the benefits of arms control cooperation.

Can New START be Saved?

The US and Russia could retain the transparency, predictability and restraint codified in New START if they negotiated a new comprehensive treaty. This would help them manage their nuclear competition in the near-term and avoid miscalculations and worst-case assessments about future intentions.

But the two nations have outlined different priorities for arms control that could slow or stall the negotiations. During the Biden Administration, the US wanted to limit the same systems covered under new START while also limiting Russia’s new kinds of nuclear delivery systems and addressing Russian theatre-range nuclear weapons. In contrast, Russia wanted to limit US ballistic missile defence programs, nonnuclear long-range delivery systems like US sea-launched cruise missiles and British and French nuclear forces. Moreover, the US would likely seek an agreement that could balance US interests in restraining Russian forces with US plans to increase the size of its own force in response to the growing requirements for nuclear deterrence.

In the absence of a new agreement, the US and Russia could agree to maintain their forces within the New START limits after the treaty expires. President Putin signalled his willingness to do this in September 2025 when he suggested that observing the treaty’s ‘central quantitative restrictions’ for another year would ‘prevent the emergence of a new strategic arms race.’

This approach, however, may not be consistent with US national security interests. President Putin did not offer to resume the data exchanges and notifications that Russia suspended in 2023, even though their absence has undermined US confidence in its ability to monitor Russia’s forces. Moreover, this proposal would delay any US plans to restore warheads to missiles limited under New START as part of its response to the growth in China’s nuclear arsenal and the emerging ‘two-nuclear peer’ environment.

Restarting Arms Control Without New START

During his early months in office, President Trump said that he would like to pursue ‘denuclearisation’ with Russia and China to reduce the ‘tremendous amounts of money’ each nation spends on nuclear forces. A pause in nuclear arms control, as recommended by many in the US policy community, would presumably be inconsistent with this goal.

Therefore, the US, Russia and China could consider a new two-track approach to manage their nuclear competition and reduce the risk of nuclear war. On the first track, President Trump, President Putin and President Xi could address broad principles of nuclear stability and restraint. On the second track, an expert working group could identify discrete sources of instability and craft concrete measures to mitigate nuclear risks.

The high-level engagement on the first track would allow the US, Russia and China to replicate some of the statements on the dangers of nuclear war that the US and Soviet Union signed during the Cold War. For example, the US and Soviet Union recognised ‘the devastating consequences that nuclear war would have for all mankind’ and their role in exerting ‘every effort to avert the risk of outbreak of such a war’ in the 1971 Accident Measures Agreement. Presidents Reagan and Gorbachev issued their famous statement that ‘a nuclear war cannot be won and must never be fought’ in 1985; the US, Russia, China, France and the UK reaffirmed this principle in early 2022.

These types of statements could begin a process of engagement and understanding that might set a baseline for more comprehensive negotiations in the future. They would not produce formal treaties, but they could provide the Presidents with an opportunity to sign joint statements that recorded their shared understanding of the risks of nuclear war.

The working-level engagement on the second track would likely revisit risk reduction concepts that the US and Soviet Union pursued during the Cold War – like enhanced communication networks, missile launch notification agreements and rules of the road to avoid military accidents and escalation. The US and China lack a similar history, but a new dialogue could open doors to better understanding and broader cooperation in identifying and responding to sources of risk in the current security environment. Bringing these discussions into a three-party working group will give each nation the opportunity to air its concerns about these sources of risk, even if they do not agree on who is responsible for the problems.

These two tracks will not address the growth in Russian and Chinese nuclear forces or interfere with US plans to modernise and expand its nuclear forces, but they might reset the arms control process and build a foundation for future talks. Moreover, they will offer a venue for the three leaders to demonstrate their commitment to reducing the risk of nuclear war and provide an opportunity for the three nations to find common ground on issues where they can cooperate to manage their nuclear competition.

© RUSI, 2025.

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