Time is running out: New START, the last remaining nuclear arms reduction treaty between the United States and Russia, is due to expire at the end of Wednesday. World leaders, including Pope Leo XIV, have publicly urged that the agreement be extended or preserved.
New START — the Strategic Arms Reduction Treaty signed by Barack Obama and Dmitry Medvedev in 2010 — caps deployed strategic nuclear warheads at 1,550 for each side and limits deployed strategic delivery vehicles and systems (heavy bombers, intercontinental ballistic missiles and submarine-launched ballistic missiles) to 800 each. The treaty also established mutual inspections and data exchanges to verify compliance. Its roots trace back to earlier Cold War-era accords, including the SALT I talks of 1972 and prior START agreements.
Originally intended to last ten years and expire in February 2021, New START was extended by five years in an arrangement between US President Joe Biden and Russian President Vladimir Putin, moving the current deadline to 2026. If the treaty lapses, the two largest nuclear powers would no longer be bound by those numerical limits. Kremlin spokesperson Dmitry Peskov warned that such an outcome would be “very bad for global security.” Analysts say the loss of transparency and inspection measures could revive an unchecked arms race, increase uncertainty and weaken crisis stability.
In September 2025, President Putin offered that Russia would unilaterally adhere to the treaty for an additional year to allow time for negotiations; then-US President Donald Trump called the proposal “sounds like a good idea,” but remained non-committal. By January 2026, Trump told the New York Times, “if it expires, it expires,” adding he expected “we’ll just do a better agreement.” Trump has argued any new deal should include China, which has substantially expanded its own arsenal.
Relations between Moscow and Washington have been strained since Russia’s full-scale invasion of Ukraine in 2022, but the conflict did not immediately terminate New START. Several months into the war Russia barred US inspections at strategic sites, and in 2023 Moscow announced it was suspending participation in the treaty, citing US support for Ukraine. Despite that suspension, Russia has reportedly continued to respect the treaty’s numerical limits.
The treaty’s history is also linked to Ukraine: under START-era arrangements, Ukraine transferred Soviet-era nuclear warheads to Russia in exchange for security assurances from Russia, the United States and the United Kingdom under the Budapest Memorandum — assurances that have since been the subject of controversy.
China complicates future negotiations. Beijing, estimated to possess about 600 nuclear warheads, has rejected proposals to cap its arsenal, saying it remains small compared with US and Russian stockpiles. Washington’s insistence that China be part of any successor deal makes a straightforward extension of New START less likely.
Technological and strategic changes further strain the treaty’s scope. Russia has deployed nuclear-capable systems not covered by New START — including hypersonic missiles and the Poseidon nuclear-capable underwater drone — while US proposals such as a planned space-based missile defense system nicknamed the “Golden Dome” have been criticized for undermining mutual vulnerability that underpins deterrence. Russian officials have warned that deployment of missile defenses on places like Greenland would provoke military responses.
Europe is watching closely. The treaty’s possible expiry has raised concerns about the reliability of the US nuclear umbrella and renewed debate over European nuclear arrangements. Some have suggested France and the UK could extend protection to other European states; German Chancellor Friedrich Merz has confirmed such discussions are taking place, though he said “the time is not right yet.” Important questions remain about command-and-control and decision-making over nuclear use. Russia has argued any new treaty should include British and French arsenals as well.
Former and current leaders have urged action. Barack Obama called on the US Congress to preserve New START, warning expiry would “pointlessly wipe out decades of diplomacy and could trigger a new arms race that would make the world less safe.” Dmitry Medvedev, deputy chairman of Russia’s National Security Council, said the end of the treaty should “alarm everyone” and warned that without alternatives the “Doomsday Clock” could accelerate.
Despite offers of unilateral adherence and public appeals for extension, differences over China’s inclusion, emerging weapons systems, missile defense and deep mutual mistrust make a simple renewal uncertain. The treaty’s expiration would mark a significant shift in the post–Cold War arms control architecture and create fresh risks for global security.
This article was translated from German.