The expiration of the U.S.-Russia New Strategic Arms Reduction Treaty (New START) has ushered in a new era of nuclear uncertainty, leaving the world’s two largest nuclear powers without any binding limits, inspections or transparency measures governing their strategic arsenals for the first time in more than five decades.
New START formally lapsed on Thursday after the White House allowed the agreement to expire without renewal or replacement. No negotiations are currently underway to establish a successor framework, raising concerns among analysts and international bodies about the growing risk of a renewed nuclear arms race.
The United States and Russia together possess about 87 percent of the world’s nuclear weapons. Since entering into force in 2011 and being extended in 2021 for five years, New START has been regarded as the last remaining pillar of bilateral nuclear arms control. The treaty capped each side at 1,550 deployed strategic nuclear warheads and imposed limits on delivery systems such as intercontinental ballistic missiles, submarine-launched ballistic missiles and heavy bombers, while providing for on-site inspections and data exchanges.
U.S. President Donald Trump dismissed the agreement as flawed, describing it on his Truth Social platform as a “badly negotiated deal” that was “being grossly violated.” He argued that extending New START would not serve U.S. interests and instead called for a “new, improved, and modernized treaty” better suited to current strategic realities.
Russia’s Foreign Ministry confirmed that it considers both sides no longer bound by any obligations under the treaty following its expiration. Moscow has previously signaled that it might observe core limits temporarily, but only under certain conditions, underscoring the fragility of any informal restraint.
Trump’s stance reflects a broader skepticism toward arms control agreements. During his first term, the United States withdrew from the Intermediate-Range Nuclear Forces Treaty in 2019, arguing that it no longer constrained adversaries effectively. Analysts say the decision to let New START lapse may indicate Washington’s desire for greater flexibility to expand or modernize its nuclear forces beyond existing limits.
Security experts warn that the loss of New START removes the last guardrail preventing unchecked nuclear competition between Washington and Moscow. Jennifer Kavanagh, a senior fellow at Defense Priorities, said the administration’s approach could signal plans to exceed previous caps on warheads and launchers, increasing the risk of escalation and miscalculation.
The treaty’s expiration has wider global implications. Without legally binding verification mechanisms, mistrust between nuclear powers is likely to deepen, potentially weakening the broader non-proliferation regime. Analysts also warn that nuclear weapons may increasingly be used as political leverage, unsettling U.S. allies and complicating extended deterrence commitments.
Russia has expressed concern about the erosion of arms control, with senior officials warning that the collapse of agreements reflects a breakdown in trust. Russian Security Council Deputy Chairman Dmitry Medvedev said the absence of agreements indicates that confidence between major powers has been exhausted.
The United Nations has also voiced alarm. Secretary-General António Guterres described the lapse of New START as a grave moment for international peace and security, warning that the risk of nuclear weapon use is now higher than at any time in decades.
Arms control experts caution that negotiating a new treaty under current geopolitical tensions will be extremely difficult. The end of New START, they argue, not only removes critical safeguards but also undermines decades of diplomacy aimed at reducing the threat of nuclear catastrophe.
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