Background and basic terms
New START was signed in 2010 by then-U.S. President Barack Obama and Dmitry Medvedev, who served one presidential term in Russia and was described at the time as an ally of Vladimir Putin. The pact entered into force the following year during a period in which relations between Moscow and Washington were described as undergoing a "reset."
The treaty set clear numerical ceilings on what are classed as strategic nuclear forces - those long-range weapons designed to strike an adversary’s principal political, military and industrial centres. Under its terms, each side is limited to no more than 1,550 deployed strategic warheads. The treaty also caps deployed delivery systems at 700, a figure that covers ground- or submarine-launched missiles and heavy bomber aircraft, and places a ceiling of 800 on launchers.
Verification and the suspension of inspections
To provide confidence that both sides were observing these limits, New START included a regime of short-notice, on-site inspections. Those measures were intended to allow each party to confirm the other’s compliance in a timely way.
Inspection activity has, however, been disrupted. Participation by Russia was suspended in 2023 in response to U.S. support for Ukraine, a move by Moscow that halted the treaty’s on-the-ground verification. Inspections had already been paused earlier during the COVID pandemic. With the verification regime not operating, the two sides have had to rely on their own intelligence assessments. Notably, despite the suspension of inspections, neither party has publicly accused the other of exceeding the treaty’s warhead limits, which formally remain in force.
Can the treaty be extended?
The treaty text itself restricts extensions - it can be extended only once. That single permitted extension was used in 2021, shortly after Joe Biden became U.S. president. With the approaching expiration date on February 5, Vladimir Putin suggested last September that the United States and Russia should informally agree to continue adhering to the treaty’s numerical limits for another year. According to available reporting, U.S. President Donald Trump has not yet given a formal reply to that proposal.
Within U.S. policy debates there are competing arguments about whether to accept such an informal arrangement. Supporters argue that an agreement to stick to the limits would demonstrate the political will to avoid an arms race and would buy time to determine next steps. Opponents contend that the United States should seize the opportunity to free itself from New START constraints now, arguing this would allow a buildup in response to an accelerating Chinese nuclear program and that acquiescing would signal weakness. These opposing views have yet to produce a definitive decision as of the treaty’s expiry deadline.
Why the treaty’s lapse matters
If the mutual observance of limits on long-range nuclear arsenals ends, it would mark the close of more than half a century of constraint on strategic nuclear weapons between the two powers. The expiration of New START would leave a gap because there have been no talks to agree a successor arrangement. Advocates of arms control warn that this creates heightened nuclear risks, particularly at a time of increased international tension related to wars in Ukraine and the Middle East.
Experts emphasize that treaties like New START provide value beyond simple numeric ceilings. They create a framework of stability and transparency intended to prevent arms races from spiralling out of control. Without that structured framework, there is concern that both sides could make worst-case assumptions about each other’s plans and respond by expanding arsenals.
What might happen if there is no replacement?
In the absence of a successor agreement, each country would be free to increase missile counts and place additional strategic warheads on deployment. Experts note, however, that such expansion faces technical and logistical constraints and would not be instantaneous - meaningful changes would take at least much of a year to implement. Over a longer time horizon, the central worry is that an unregulated arms race would develop, with each side repeatedly adding weapons based on the other side’s perceived intentions.
What would a successor treaty need to address?
U.S. political leaders have stated a desire for a new and improved accord, but specialists caution that negotiating a successor would be a lengthy and technically demanding process. Any new deal would likely need to consider other kinds of nuclear systems not covered in the original treaty text, such as short- and intermediate-range weapons, as well as novel and unconventional platforms that Russia has developed since New START was concluded - examples of which include the Burevestnik cruise missile and the Poseidon nuclear-capable torpedo.
Negotiators would also face disputes over who should be party to future talks. While the stated aim by some U.S. leaders has been to pursue denuclearisation discussions that include both Russia and China, Beijing has said it is unrealistic to expect it to join three-way negotiations with states whose arsenals remain far larger than its own. Russia has argued that the nuclear forces of NATO members Britain and France should be included in any talks - a proposition those countries reject. These competing positions complicate prospects for reaching a multilateral deal.
Bottom line
With New START’s legal extension already used, the treaty’s set-to expiry on February 5 leaves a narrow window for leaders to agree on whether to observe its limits informally while pursuing a successor. Without that pause, the two leading nuclear powers face a future in which agreed numerical ceilings and an on-site verification framework no longer govern their strategic arsenals, a development that analysts say raises the risk of an escalating, unregulated arms competition - a process that would unfold over months to years rather than overnight.