U.S.–Russia Nuclear Rearmament: The Risk of a Lapsed New START

The United States and Russia are approaching a critical arms control deadline with no clear path to a successor agreement.

The New START treaty, the last remaining bilateral nuclear arms control agreement between Washington and Moscow, is set to expire in February 2026. Talks on replacement arrangements have stalled, and formal inspections under the treaty remain suspended. If the agreement lapses, it would mark the first time since the early 1970s that the two countries are without legally enforceable caps on deployed strategic warheads and delivery systems.

New START limits each side to 1,550 deployed strategic nuclear warheads and 700 deployed delivery systems, and provides for verification measures that have long been seen as a stabilising feature of U.S.–Russian relations. 

Its potential expiration comes after years of erosion in the global arms control framework, including the collapse of the Intermediate-Range Nuclear Forces Treaty and the deterioration of relations following Russia’s invasion of Ukraine.

Kremlin spokesman Dmitry Peskov said this week that the world would become “more dangerous” without the treaty. In the U.S., U.S. President Donald Trump has argued that the expiration of New START would open the door to negotiating a broader or improved agreement, though U.S. officials have acknowledged that no substantive talks are currently under way.

At the height of the Cold War, global nuclear arsenals exceeded 70,000 warheads. Today, the total stands at around 12,500, according to open-source estimates, with the steepest reductions achieved through successive U.S.–Soviet and U.S.–Russian treaties. 

Arms control experts warn that the loss of New START would not immediately lead to a rapid build-up, but would remove transparency and predictability at a moment of growing strategic competition.

Pope Leo’s appeal

The looming expiry has also drawn international concern. Pope Francis has renewed calls for nuclear disarmament, urging world leaders not to allow existing arms control instruments to lapse without credible follow-up. He warned that abandoning such frameworks risks accelerating an arms race and further undermining global security.

A shifting nuclear landscape

Beyond the U.S. and Russia, seven other states possess nuclear weapons: China, France, the United Kingdom, India, Pakistan, Israel and North Korea. China’s rapid modernization has drawn particular attention. 

According to the Stockholm International Peace Research Institute, Beijing has more than doubled its nuclear arsenal since 2020 and could reach around 1,000 warheads by the mid-2030s, although it remains well below U.S. and Russian levels.

India and Pakistan continue to expand their arsenals at a steady pace, driven by regional tensions, while North Korea is consolidating its capabilities and doctrine. In Europe, France and the United Kingdom are investing in the long-term credibility of their nuclear forces within NATO, which continues to treat nuclear deterrence as central to collective defence.

SIPRI has warned that the weakening of arms control regimes risks ushering in a new phase of nuclear competition, even if overall warhead numbers remain below Cold War peaks.

Pressure on non-proliferation

The broader non-proliferation system is also under strain. Iran’s nuclear programme remains a central concern, with enrichment levels and reduced transparency fueling debate over potential breakout capacity. 

Saudi Arabia has indicated interest in nuclear capabilities in response to regional rivals. In Germany, Japan and South Korea, long-standing non-nuclear policies are increasingly debated amid shifting security assumptions.

Within the European Union, governments continue to balance support for the Nuclear Non-Proliferation Treaty with reliance on NATO’s nuclear deterrence. The 2026 NPT Review Conference is expected to test that balance.