The Nato secretary general, Jens Stoltenberg, has indicated that the military alliance is considering whether to increase the number of available nuclear weapons, triggering warnings from experts about the possibility of a new arms race. Stoltenberg said Nato could, for the first time, face a significant nuclear threat from two fronts – Russia and China – and that it may be necessary to increase the number of deployable warheads as a deterrent. Speaking to the Telegraph on Sunday, Stoltenberg said: “I won’t go into operational details about how many nuclear warheads should be operational and which should be stored, but we need to consult on these issues. That’s exactly what we’re doing.” Though the remarks were deliberately cautious, they echo comments from the White House a week before, warning about a perceived need to respond to increases in warhead numbers from China, Russia and North Korea. Pranay Vaddi, the top national security council arms control official, said this month: “Absent a change in adversary arsenals, we may reach a point in the coming years where an increase from current deployed numbers is required”. One analyst said Stoltenberg, visiting the US on Monday, appeared to be amplifying American messaging aimed at Moscow and Beijing, although Nato has historically not been focused on China. Sebastian Brixey-Williams, the executive director of the Basic security thinktank, said: “I read it at this stage as a form of signalling intended to sober up Russia and China in order to try to avert an arms race. But we should not assume it is a bluff, and it may in fact make an arms race more likely.” Next month Nato hosts its annual summit in Washington DC against a backdrop of a US election. The challenger Donald Trump has repeatedly voiced scepticism about the value of the alliance and complained about levels of defence spending by its mostly European members. In advance of a trip to the White House, Stoltenberg said countries’ defence spending had increased significantly in the past year. “I can already now reveal that this year more than 20 allies will spend at least 2% of GDP on defence,” he said in a speech in the US capital, compared with 11 countries 12 months ago. The US has 1,770 nuclear warheads placed on missiles or located on bases with operational forces, according to figures compiled by the Stockholm International Peace Research Institute (Sipri) earlier on Monday. Russia retains 1,710, and has suspended cooperation with the New Start treaty that it signed with the US, intended to set a ceiling on the number of strategic warheads deployed at 1,550. Tactical or battlefield nuclear weapons are not counted towards the New Start limit. China is believed to have started deploying a small number of nuclear weapons with their launchers during 2023 – a total of 24, according to the Sipri research – and there are concerns in Washington and Nato that Beijing could lift the total significantly. Stoltenberg said that “in a not very distant future” Nato “may face something that it has never faced before, and that is two nuclear-powered potential adversaries – China and Russia. Of course, this has consequences.” Concerns about the China’s long-term nuclear programme at a time of Russian military aggression are said to have contributed to the UK’s decision to lift a cap on the maximum number of Trident warheads it is willing to hold from 180 to 260. About 120 are operational deployable on nuclear submarines, Sipri estimates. Nuclear warheads vary in their destructive power but most have the capability to destroy cities. Trident warheads are each estimated to have an explosive power of 100 kilotons; the atomic bomb dropped on Hiroshima in 1945 at the end of the second world war was about 15 kilotons. Dmitri Peskov, a spokesperson for the Kremlin, accused Stoltenberg of “another escalation of tension”, while a Nato spokesperson sought to downplay the secretary general’s comments by emphasising that beyond modernisation there were “no significant changes to our nuclear deterrent”. British defence sources said the UK was not involved in discussion about changes to its operational nuclear deployment. The UK’s nuclear weapons are committed to the defence of Nato in the event of a major military crisis, while the US has pledged to come to the aid of alliance members if attacked.