The landmark New Start treaty between the United States and Russia officially expired on Thursday, ending decades of nuclear restraint and leaving both countries free to expand their strategic arsenals without legal limits.
Signed more than half a century ago during the Cold War era, New Start capped each side’s missiles, launchers, and strategic warheads, providing predictability and transparency that prevented an unchecked nuclear arms buildup.
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Russian President Vladimir Putin had proposed a one-year extension of the treaty’s core provisions, but US President Donald Trump did not respond formally, instead seeking a broader deal that would include China, which has refused participation.
Moscow criticised Washington’s approach, calling it “mistaken and regrettable,” and warned that Russia remains prepared to take decisive military-technical measures while remaining open to diplomacy for stabilising the strategic situation.
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Analysts warn the treaty’s lapse could spark a new arms race, with each country potentially deploying hundreds of additional warheads beyond the previous limit of 1,550, while artificial intelligence and new technologies add unpredictability to escalation dynamics.
UN Secretary-General Antonio Guterres described the situation as the highest nuclear risk in decades, urging both nations to resume negotiations promptly to establish a successor framework that restores verifiable limits and strengthens global security.