Combine three wary nations, deep historical mistrust, rapid technological change, the most destructive weapons ever developed and a US unwilling to extend Thursday’s last formal nuclear weapons guardrail, and you have the ingredients for much worse geopolitical tension, if not a slide towards global disaster, warn nuclear weapons negotiators, analysts and former government officials.

“Rather than extend ‘NEW START’ (A badly negotiated deal by the United States that, aside from everything else, is being grossly violated), we should have our Nuclear Experts work on a new, improved, and modernised Treaty that can last long into the future,” Trump said on Thursday on social media.

But experts fear that could spell the death of arms control efforts at a time of great global tension, given the president’s other priorities and short attention span. This week, for the first time in half a century, the world is without a legally binding agreement to hold nuclear weapons in check.

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Trump orders US military to resume nuclear weapons tests for first time in 33 years

Trump orders US military to resume nuclear weapons tests for first time in 33 years

“There is growing pressure in the United States to build up the US arsenal in response to a variety of factors, including the build-up of China’s arsenal,” said James Acton, nuclear policy co-director with the Carnegie Endowment for International Peace.A worst-case scenario sees a US nuclear build-up prompting Russia to respond, Acton said, heaping pressure on China to accelerate its expansion, causing the US to bolster its weapons cache as the downward spiral continues. “We are on the verge of a new arms race,” he added.