The New START Treaty between the United States and Russia officially expired on February 5, 2026, marking the end of the last binding limits on their strategic nuclear arsenals. This milestone ends over 50 years of bilateral arms control agreements that helped stabilize global nuclear risks since the Cold War era.

What Was the New START Treaty?

Signed in 2010 by Presidents Barack Obama and Dmitry Medvedev, the New Strategic Arms Reduction Treaty (New START) entered into force on February 5, 2011. It capped deployed strategic nuclear warheads at 1,550 per side and limited deployed delivery systems (such as intercontinental ballistic missiles, submarine-launched ballistic missiles, and heavy bombers) to 700. The treaty included robust verification measures, including data exchanges and on-site inspections, to build transparency and reduce the risk of miscalculation.

A five-year extension was agreed upon in 2021, pushing the expiration to February 5, 2026 (with some sources noting February 4 as the final full day in force). Unlike previous treaties, no further extension was possible without a new agreement or re-ratification.

UN Secretary-General’s Stark Warning

UN Secretary-General António Guterres described the expiration as a “grave moment” for international peace and security. In his statement on February 5, 2026, he highlighted that, for the first time in more than half a century, the world faces no legally binding limits on the strategic nuclear arsenals of the U.S. and Russia—which together possess the vast majority of global nuclear weapons.

Guterres warned that this comes amid heightened global tensions, where the risk of nuclear weapon use is at its highest in decades. He urgently called for both nations to return to the negotiating table without delay to establish a successor framework that restores verifiable limits, reduces risks, and strengthens collective security.

Reactions from the U.S. and Russia

Both countries expressed regret over the lapse but emphasized openness to future dialogue. The U.S. side, under President Donald Trump, has signaled interest in pursuing a new, “modernized” pact. Trump stated that rather than extending the “badly negotiated” New START—which he claimed was being violated—he directed nuclear experts to work on an improved treaty for the long term. He has previously advocated for including China in any new agreement, though Beijing has shown reluctance.

Russia, for its part, had proposed informally adhering to the limits for an additional year post-expiration if reciprocated, but with no formal U.S. acceptance, it declared the obligations no longer binding while remaining open to talks under suitable conditions.

Why This Raises Global Nuclear Risks

The expiration removes verifiable caps and transparency mechanisms, potentially paving the way for an unchecked buildup of strategic weapons. Arms control experts and advocates fear this could spark a renewed nuclear arms race, especially as Russia modernizes its forces and concerns grow over emerging nuclear powers.

With no bilateral guardrails in place, the risk of escalation in ongoing conflicts or misperceptions increases. International observers, including China (which called the expiration regrettable), have urged resumed dialogue on strategic stability.

What’s Next?

While the immediate post-expiration period brings uncertainty, statements from both Washington and Moscow suggest potential for negotiations toward a successor agreement. However, deep geopolitical divides—including the Ukraine conflict and broader strategic competition—complicate prospects.

The end of New START underscores the fragility of nuclear arms control in a multipolar world. As UN chief Guterres emphasized, swift action is essential to prevent a dangerous new era of unconstrained nuclear competition.

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