CHATHAM HOUSE - The US and Russia’s nuclear weapons treaty is set to expire. Here’s what’s at stake - Letting New START expire would signal that the world’s largest nuclear powers are abandoning restraint. Expert comment Published 26 January 2026 — 4 minute READ Image — US President Donald Trump welcomes Russian President Vladimir Putin for talks on Ukraine in Anchorage, Alaska, on 15 August 2025. Photo by Contributor/Getty Images. Georgia Cole Research Associate, International Security Programme On 4 February 2026, the New Strategic Arms Reduction Treaty (New START) is due to expire. If it does, it will mark the first time since the early 1970s that there will be no legally binding limits on US and Russian strategic nuclear forces without another agreement being under negotiation. This would mark a significant break in more than five decades of bilateral nuclear arms control. It would also signal a move away from nuclear restraint, making the world a more dangerous place. New START weakened, but still consequential New START was signed in 2010 by President Obama and President Medvedev. The treaty caps the US and Russia each at 1,550 deployed strategic nuclear warheads, 800 deployed and non-deployed strategic launchers, and up to 700 deployed intercontinental ballistic missiles, submarine-launched ballistic missiles, and heavy bombers. It also established detailed transparency and verification mechanisms, including data exchanges, notifications and on-site inspections. The treaty built on earlier agreements that drove large reductions in Cold War arsenals. It was designed for a 10-year term from 2011 with the option of a single five-year extension, which was agreed at the final hour in 2021. Its provisions do not allow for a further formal extension. Putin suspended Russia’s participation in the treaty in February 2023, with the US following suit. This put an end to mutual inspection visits and data exchanges. However, both sides have continued to signal that they are adhering to the treaty’s core numerical limits and there is no evidence of large-scale breaches. This suggests that even in weakened form, New START has retained political and practical value. The agreed limitations still reinforce strategic stability, and the expectation of compliance still shapes behaviour. This makes the prospect of expiry even more consequential. The move would not simply formalize the end of a treaty that is no longer operational. It would remove the last agreed framework governing the size of the two largest nuclear arsenals worldwide. The politics of extension In September 2025, Putin proposed a one-year voluntary extension of New START’s central limits. At the time, Trump said it ‘sounds like a good idea’, but no formal negotiations have followed. Moscow recently indicated that it no longer has clear interlocutors within the US administration to reach out to regarding its extension offer. Trump has also recently suggested that if New START expires, a ‘better’ agreement could be negotiated and said that China should be included. Of course, broader participation in arms control would be desirable in principle. But in practice, making Chinese involvement a precondition for progress risks ensuring no limits at all. Beijing has consistently argued that it will not join formal arms control negotiations while its arsenal remains far smaller than those of the US and Russia. China is estimated to have a nuclear arsenal of 600 warheads, while Russia and the US each have inventories of over 5,000 warheads. Other nuclear-armed states will be watching closely. The strategic environment is further complicated by US plans to accelerate its advanced missile defence capabilities, including against nuclear weapons, under the ‘Golden Dome’. Moscow has long linked offensive nuclear limits to constraints on US missile defence. An accelerated push by the US to enhance its missile defences, combined with the disappearance of New START’s constraints, risks reinforcing Russian (and Chinese) incentives to expand and diversify their offensive arsenals, fuelling arms race dynamics. Negotiating a new treaty from scratch would be a major undertaking even in a more stable political environment. It requires technical work on definitions, counting rules and verification. It also needs sustained diplomatic engagement and a degree of trust. None of these conditions are currently in place. The idea that a comprehensive successor could be concluded quickly is unrealistic. A one year-extension of limits, even without full restoration of verification measures, would be imperfect. But it would preserve some predictability while buying time. The alternative is a rapid move to an unconstrained environment in a time of heightened geopolitical rivalry. What expiry would mean Without the New START limits, strategic planning on both sides is more likely to be driven by uncertainty and worst-case assessments. That increases the risk of a new arms race, especially if either side begins uploading additional warheads onto existing missiles or expanding delivery systems. Even if large-scale build-ups do not occur immediately, the absence of limits and transparency will make intentions harder to read and crises harder to manage. Related work Russia and the US put nuclear testing back on the table. Is time running out for arms control? The implications extend beyond the bilateral relationship. China is already expanding and modernizing its nuclear forces. The removal of any constraints on the US and Russia’s nuclear arsenals weakens the argument for restraint elsewhere and reinforces the view that major powers are moving back towards open-ended competition. Other nuclear-armed states will be watching closely. Timing also matters. The expiry comes ahead of the 2026 Review Conference of the Nuclear Non-Proliferation Treaty (NPT) in spring. Nuclear-weapons states are expected to demonstrate progress on disarmament and arms control. The disappearance of the last US-Russia treaty without replacement would signal the opposite – that nuclear powers are abandoning restraint. That could deepen divisions between nuclear and non-nuclear states and weaken the credibility of the NPT. Managing risk without a treaty Even if New START expires, there are steps that can reduce risk and prevent a complete collapse of nuclear restraint. The permanent five nuclear-weapons-states (P5) should establish sustained high-level engagement focused on risk reduction, confidence-building measures and strategic stability. This does not require immediate negotiations on formal limits. Regular exchanges on doctrine, perceptions and emerging technologies can still lower the risk of miscalculations. Secure and reliable communication channels should be strengthened and, where possible, broadened. Direct lines between the US and Russia remain essential, but crisis communication involving other P5 states (i.e. between the UK, France, and Russia; or the US and China) would help manage crises which involve multiple nuclear-armed states. Topics Arms control Regions United States of America Russia Departments International Security Programme Consultative mechanisms similar to those under New START should be maintained or recreated in some form. The treaty’s bilateral forums provided a structured space to raise compliance concerns and discuss new systems. This should continue as a useful mechanism for dialogue, particularly on missile defence and the implications of the Golden Dome. Other states should use multilateral settings, including the NPT Review Conference, to clearly signal that the erosion of arms control is not a purely bilateral issue. Coordinated diplomatic pressure can raise the political costs of abandoning restraint. At the same time, coordinated statements between P5 members can show a commitment to progress and hopefully set the scene for future arms control. President Biden and President Xi agreeing in November 2024 to not use AI in nuclear command and control is a good example. Arms control also cannot be separated from the broader security environment. Progress on major conflicts, including in Ukraine, would make it easier to rebuild the political will for more ambitious agreements in future. A narrowing margin for error New START was never a comprehensive solution to US-Russia strategic rivalry, and parts of its framework reflect an earlier phase of nuclear competition. But it has provided a foundation of predictability in a deteriorating relationship. Allowing it to expire would remove that foundation. In the current geopolitical climate, the margin for error is already small. Preserving some form of mutual restraint – however limited – remains preferable to risking the dangerous instability of unconstrained nuclear competition.

 CHATHAM  HOUSE 

The US and Russia’s nuclear weapons treaty is set to expire. Here’s what’s at stake

Letting New START expire would signal that the world’s largest nuclear powers are abandoning restraint.

Expert comment

Published 26 January 2026 —

4 minute READ

Image — US President Donald Trump welcomes Russian President Vladimir Putin for talks on Ukraine in Anchorage, Alaska, on 15 August 2025. Photo by Contributor/Getty Images.

Georgia Cole

Research Associate, International Security Programme

On 4 February 2026, the New Strategic Arms Reduction Treaty (New START) is due to expire. If it does, it will mark the first time since the early 1970s that there will be no legally binding limits on US and Russian strategic nuclear forces without another agreement being under negotiation. 

This would mark a significant break in more than five decades of bilateral nuclear arms control. It would also signal a move away from nuclear restraint, making the world a more dangerous place.

New START weakened, but still consequential 

New START was signed in 2010 by President Obama and President Medvedev. The treaty caps the US and Russia each at 1,550 deployed strategic nuclear warheads, 800 deployed and non-deployed strategic launchers, and up to 700 deployed intercontinental ballistic missiles, submarine-launched ballistic missiles, and heavy bombers. It also established detailed transparency and verification mechanisms, including data exchanges, notifications and on-site inspections.

The treaty built on earlier agreements that drove large reductions in Cold War arsenals. It was designed for a 10-year term from 2011 with the option of a single five-year extension, which was agreed at the final hour in 2021. Its provisions do not allow for a further formal extension.

Putin suspended Russia’s participation in the treaty in February 2023, with the US following suit. This put an end to mutual inspection visits and data exchanges.

However, both sides have continued to signal that they are adhering to the treaty’s core numerical limits and there is no evidence of large-scale breaches. This suggests that even in weakened form, New START has retained political and practical value. The agreed limitations still reinforce strategic stability, and the expectation of compliance still shapes behaviour.

This makes the prospect of expiry even more consequential. The move would not simply formalize the end of a treaty that is no longer operational. It would remove the last agreed framework governing the size of the two largest nuclear arsenals worldwide. 

The politics of extension

In September 2025, Putin proposed a one-year voluntary extension of New START’s central limits. At the time, Trump said it ‘sounds like a good idea’, but no formal negotiations have followed. Moscow recently indicated that it no longer has clear interlocutors within the US administration to reach out to regarding its extension offer. 

Trump has also recently suggested that if New START expires, a ‘better’ agreement could be negotiated and said that China should be included. Of course, broader participation in arms control would be desirable in principle. But in practice, making Chinese involvement a precondition for progress risks ensuring no limits at all. Beijing has consistently argued that it will not join formal arms control negotiations while its arsenal remains far smaller than those of the US and Russia. China is estimated to have a nuclear arsenal of 600 warheads, while Russia and the US each have inventories of over 5,000 warheads. 

Other nuclear-armed states will be watching closely.

The strategic environment is further complicated by US plans to accelerate its advanced missile defence capabilities, including against nuclear weapons, under the ‘Golden Dome’. Moscow has long linked offensive nuclear limits to constraints on US missile defence. An accelerated push by the US to enhance its missile defences, combined with the disappearance of New START’s constraints, risks reinforcing Russian (and Chinese) incentives to expand and diversify their offensive arsenals, fuelling arms race dynamics.

Negotiating a new treaty from scratch would be a major undertaking even in a more stable political environment. It requires technical work on definitions, counting rules and verification. It also needs sustained diplomatic engagement and a degree of trust. None of these conditions are currently in place. The idea that a comprehensive successor could be concluded quickly is unrealistic. 

A one year-extension of limits, even without full restoration of verification measures, would be imperfect. But it would preserve some predictability while buying time. The alternative is a rapid move to an unconstrained environment in a time of heightened geopolitical rivalry.

What expiry would mean

Without the New START limits, strategic planning on both sides is more likely to be driven by uncertainty and worst-case assessments. That increases the risk of a new arms race, especially if either side begins uploading additional warheads onto existing missiles or expanding delivery systems. Even if large-scale build-ups do not occur immediately, the absence of limits and transparency will make intentions harder to read and crises harder to manage.

Related work

Russia and the US put nuclear testing back on the table. Is time running out for arms control?

The implications extend beyond the bilateral relationship. China is already expanding and modernizing its nuclear forces. The removal of any constraints on the US and Russia’s nuclear arsenals weakens the argument for restraint elsewhere and reinforces the view that major powers are moving back towards open-ended competition. Other nuclear-armed states will be watching closely.

Timing also matters. The expiry comes ahead of the 2026 Review Conference of the Nuclear Non-Proliferation Treaty (NPT) in spring. Nuclear-weapons states are expected to demonstrate progress on disarmament and arms control. The disappearance of the last US-Russia treaty without replacement would signal the opposite – that nuclear powers are abandoning restraint. That could deepen divisions between nuclear and non-nuclear states and weaken the credibility of the NPT. 

Managing risk without a treaty

Even if New START expires, there are steps that can reduce risk and prevent a complete collapse of nuclear restraint.

The permanent five nuclear-weapons-states (P5) should establish sustained high-level engagement focused on risk reduction, confidence-building measures and strategic stability. This does not require immediate negotiations on formal limits. Regular exchanges on doctrine, perceptions and emerging technologies can still lower the risk of miscalculations.

Secure and reliable communication channels should be strengthened and, where possible, broadened. Direct lines between the US and Russia remain essential, but crisis communication involving other P5 states (i.e. between the UK, France, and Russia; or the US and China) would help manage crises which involve multiple nuclear-armed states.

Topics

Arms control

Regions

United States of America Russia

Departments

International Security Programme

Consultative mechanisms similar to those under New START should be maintained or recreated in some form. The treaty’s bilateral forums provided a structured space to raise compliance concerns and discuss new systems. This should continue as a useful mechanism for dialogue, particularly on missile defence and the implications of the Golden Dome.

Other states should use multilateral settings, including the NPT Review Conference, to clearly signal that the erosion of arms control is not a purely bilateral issue. Coordinated diplomatic pressure can raise the political costs of abandoning restraint. At the same time, coordinated statements between P5 members can show a commitment to progress and hopefully set the scene for future arms control. President Biden and President Xi agreeing in November 2024 to not use AI in nuclear command and control is a good example.

Arms control also cannot be separated from the broader security environment. Progress on major conflicts, including in Ukraine, would make it easier to rebuild the political will for more ambitious agreements in future.

A narrowing margin for error

New START was never a comprehensive solution to US-Russia strategic rivalry, and parts of its framework reflect an earlier phase of nuclear competition. But it has provided a foundation of predictability in a deteriorating relationship. Allowing it to expire would remove that foundation.

In the current geopolitical climate, the margin for error is already small. Preserving some form of mutual restraint – however limited – remains preferable to risking the dangerous instability of unconstrained nuclear competition.