The cost of the US nuclear arsenal over the next 30 years will be over $1.2tn, even before any new weapons ordered by the Trump administration, and is unlikely to be affordable without cuts elsewhere in the defence budget, according to a independent congressional report.

Trump team drawing up fresh plans to bolster US nuclear arsenal Read more

The total price tag marks nearly a 25% increase from previous estimate, taking in the modernisation programme established under the Obama administration, which accounts for $400bn, the Congressional Budget Office (CBO) found. The costs would peak in the 2020s and the 2030s.

A new Nuclear Posture Review is under way and expected around the end of the year. Trump has repeatedly vowed to bolster the nuclear stockpile, and the defence department is reportedly considering the development of a low-yield warhead for a ballistic missile, and reintroducing a sea-launched cruise missile, among a variety of new options.

The CBO report warns that such new capabilities would increase the total bill for the US arsenal yet further.

“If these plans reach fruition, it would be the largest nuclear buildup since the Reagan administration. This is not affordable,” said Stephen Schwartz, an independent nuclear analyst and editor of the book, Atomic Audit: The Costs and Consequences of US Nuclear Weapons Since 1940.

“Pursuing nuclear modernization will be challenging in the current environment,” the report said, adding that it would compete with parallel ambitions to upgrade the navy and the air force, and increase the size of the army.

It is the first comprehensive costing of the US nuclear weapons programme. The report offers three approaches for cost reductions to make it affordable. One would keep the programme as is currently planned but delay elements of it, bringing potential savings of 5%.

The second looks at ways of reducing the programme but keeping to the existing ceiling agreed with Russia of 1,550 deployed strategic warheads. One variant of that approach examined by the CBO would be to do without one leg of the nuclear “triad”, intercontinental ballistic missiles (ICBMs) and keeping air-launched and sea-launched weapons. That would generate savings of 10%, the report said.

The third approach would incorporate a reduction of the deployed strategic stockpile to 1,000 warheads, a cut the defence department under the Obama administration said could be made without affecting the US nuclear deterrent, which would save 5% to 11% of the total.

“The report blows apart the ‘do everything or do nothing’ false choice repeatedly posited by Pentagon officials,” Kingston Reif, the director for disarmament and threat reduction policy at the Arms Control Association, said. “But perhaps the biggest contribution of new CBO nuclear cost study is the evaluation of options to manage and reduce the mammoth price tag.”

Reif added: “Meanwhile, the Trump administration is reportedly considering adding new weapons to the arsenal, which would increase the budget train-wreck odds, and undermine US security.”