The New START treaty - the last remaining formal arms control agreement between Washington and Moscow that limited long-range nuclear forces - has now expired. Negotiators and analysts say the pact established both numerical caps on strategic weapons and an inspection regime designed to provide transparency. Its lapse leaves the two powers without a standing, legally binding framework that directly constrained their deployed strategic arsenals.
Origins and basic terms
New START was signed in 2010 by then-U.S. President Barack Obama and Dmitry Medvedev, who served a single presidential term in Russia and was at the time politically aligned with Vladimir Putin. The agreement entered into force the following year. At its core the treaty placed explicit limits on the strategic nuclear forces of both sides - the weapons intended for strikes on an opponent's principal political, military and industrial centers in the event of a large-scale nuclear exchange.
Under the accord, each country was restricted to no more than 1,550 deployed strategic warheads. It also capped the number of deployed delivery platforms - ground- or submarine-launched missiles and heavy bomber aircraft - at 700, and limited the number of launchers to 800.
Verification and the suspension of inspections
A central element of New START was a verification system that allowed short-notice, on-site inspections so each side could satisfy itself that the other was complying with the numerical restraints. Those inspections functioned as a confidence-building measure, reducing the need to rely solely on intelligence estimates.
That verification apparatus was already strained by interruptions: inspections were put on hold during the COVID-19 pandemic. Then in 2023, Russia under President Vladimir Putin suspended its participation in the treaty in response to U.S. support for Ukraine. That suspension halted the inspections entirely, leaving both capitals to rely on their own surveillance and intelligence to assess the other's forces. Nonetheless, both sides have stated they would continue to abide by the treaty's numerical limits up to this point.
Why a further extension was not possible
The treaty text permits only one extension. That extension was exercised in 2021, shortly after Joe Biden assumed the U.S. presidency. With the agreement now expiring, Russian President Putin proposed in September that Washington and Moscow informally adhere to the same warhead limits for an additional year. As of the treaty's final day, U.S. President Donald Trump had not accepted that informal proposal.
Within U.S. political and policy circles there is no consensus on whether the informal adherence to limits should have been accepted. Supporters of acceptance argued it would have signaled political will to avoid a renewed arms race and provided breathing room to negotiate a more comprehensive successor. Opponents contended that adherence would prevent the United States from responding to a rapid Chinese nuclear buildup and could be interpreted as a sign of weakness.
Consequences of the lapse
With the treaty expired, formal mutual limits on long-range nuclear arsenals are no longer in force. That development represents the end of more than fifty years of bilateral constraints on these classes of weapons that had been maintained in various incarnations of arms control agreements.
Arms control advocates warn the lapse creates a transparency void and increases nuclear risks, particularly at a time when international tensions are elevated due to the wars in Ukraine and the Middle East. Experts stress that the value of such treaties goes beyond setting numerical ceilings; they provide a predictable, verifiable framework that helps to prevent arms races from escalating on worst-case assumptions.
What could both sides do without the treaty?
In the absence of binding limits, each country would be free to increase missile inventories and to deploy additional strategic warheads. Analysts note, however, that significant expansions face technical and logistical constraints and would not occur overnight. Substantial changes to deployed forces would likely take at least many months, and more realistically the better part of a year, to implement at scale.
Over a longer horizon, the principal concern is that an unregulated competition could develop in which both sides continually add systems based on the worst plausible assumptions about the other's intentions and capabilities.
What would a replacement treaty require?
Although U.S. political leaders have stated a desire for a new, improved agreement, experts underline that negotiating a successor would be a long and technically complex process. A modern successor would probably have to address additional weapon classes that New START did not cover, including shorter- and intermediate-range systems as well as newer, unconventional platforms that emerged after the treaty was negotiated.
The Russian arsenal now includes systems identified as outside the original New START parameters, such as the Burevestnik cruise missile and the Poseidon torpedo. A successor deal could face further complications over who should be included at the bargaining table. U.S. officials have indicated a desire to engage Russia and China; Beijing has said it is unrealistic to ask a country with a much smaller arsenal to join talks alongside states with much larger forces. Russia has argued that the nuclear forces of Britain and France should also be part of any negotiation - a position those countries reject.
Given these technical challenges and the lack of agreement on participants, reaching a comprehensive treaty that both sides find acceptable will be difficult and time consuming.
Key takeaways
- New START set limits of 1,550 deployed strategic warheads per side and capped deployed strategic delivery systems and launchers.
- Verification relied on short-notice site inspections, but inspections were suspended during the COVID pandemic and halted completely after Russia suspended participation in 2023.
- The treaty could only be extended once - that extension occurred in 2021 - and there is no successor agreement in place following the expiry.
Sectors potentially affected
- Defense and aerospace contractors engaged in strategic delivery systems and warhead production or maintenance.
- National security and intelligence communities that monitor strategic forces and verify compliance.
- Geopolitical risk-sensitive markets that react to changes in perceived international stability.
Risks and uncertainties
- Potential for an unregulated arms buildup if both sides elect to expand their deployed strategic arsenals; this most directly affects defense suppliers and national budgets allocated to strategic forces.
- Loss of on-site inspections reduces transparency and increases reliance on intelligence assessments, raising the risk of miscalculation; this impacts intelligence operations and diplomatic channels.
- No agreement on who should participate in successor negotiations - in particular the positions of China, Britain and France - creates uncertainty about whether a comprehensive, multilateral treaty is attainable.