February 2026 saw the end of the New Strategic Arms Reduction Treaty, known as New START, the last nuclear arms control agreement between the United States and Russia. Without limitations on nuclear weapons, what comes next? Can scientists step in, as they did in years past, to help stop the risk of nuclear war?

There are now three major nuclear powers—the United States, Russia, and China—and six smaller nuclear-armed states (France, the United Kingdom, India, Pakistan, Israel, and North Korea). With the New START Treaty no longer in force, there is an opportunity for leaders of these nuclear states to create new treaties. US President Trump has said that he wants to do this and has plans to meet with China’s President Xi Jinping in 2026; he is also likely to meet Russia’s President Vladimir Putin during the year. These encounters may set nuclear negotiations back on course. But as Trump and his administration are swept into new crises in Venezuela and Iran, nuclear arms control could remain unresolved and stagnate for the remainder of his term.

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