DONALD TRUMP’S threat to resume nuclear weapons tests risks turbo-charging a new nuclear arms race that could “take the world to the brink of annihilation,” anti-nuclear campaigners and experts warned today.

The US president announced on social media today that he had ordered the Pentagon to resume nuclear weapons tests “immediately,” though he was vague when asked by reporters to clarify if he really meant nuclear-explosive testing, which the United States has not carried out since 1992.

“Because of other countries’ testing programmes, I have instructed the Department of War to start testing our nuclear weapons on an equal basis,” Mr Trump posted. It was unclear which other countries he was referring to — in remarks to reporters later on Air Force One, he mentioned the nuclear weapons stockpiles of Russia and China, but neither has tested a nuclear weapon since the 1990s.

“I see them testing and I say, well, if they’re going to test, I guess we have to test,” Mr Trump said, leading to speculation as to whether he meant actual detonations of nuclear devices or testing delivery systems — something Russia has recently done, but which is already routine for the United States as well.

“If the US restarts testing its nuclear weapons, this will accelerate a new nuclear arms race,” warned Campaign for Nuclear Disarmament general secretary Sophie Bolt.

“Recommencing atmospheric or underground testing would release huge levels of radioactive fallout into the atmosphere and land, threatening us all. It would cause cancers, leukaemias and birth defects amongst inhabitants living around test sites, like the ‘Downwinders,’ who have been exposed to radiation since the US starting testing nuclear weapons in the 1950s at its Nevada test site.”

The world’s major powers ended nuclear weapons tests in the 1990s, following decades in which evidence mounted that radioactive fallout poisoned the land and atmosphere and could cause sickness across multiple generations. Reckoning the number of lethal cancers caused by exposure to nuclear fallout is difficult, but estimates in the United States range from tens to hundreds of thousands.

Ms Bolt also warned that a resumption of nuclear tests would bring closer the risk of nuclear war.

“The consequences of a nuclear war would be absolutely catastrophic, destroying huge sections of the planet, devastating the ecosystem and creating global famine for the survivors.

“We are already in the midst of nuclear expansion as nuclear weapons states modernise and expand their nuclear weapons. It is absolutely critical that we rachet up the political pressure to make these world leaders — including the British government — step back from this nuclear escalation,” she urged.

Nuclear weapons tests are prohibited by the Comprehensive Test Ban Treaty, to which the United States is a signatory. But Mr Trump has form on ripping up arms control treaties, having withdrawn from the Intermediate Nuclear Forces treaty and the Open Skies treaty during his first term.

“Trump is playing a very dangerous game,” Stop the War Coalition convener Lindsey German told the Morning Star.

“The resumption of testing of nuclear warheads for the first time in over 30 years would send a signal that the threat of nuclear war is getting closer. It would lead to similar testing by countries such as Russia and China.

“His assertion that this is already happening is false.”

Dr David Lowry of the Institute for Resource and Security Studies agreed, saying resumed testing would “open the floodgates” to other countries detonating nuclear weapons, “though there is no military reason to do so, as no testing has taken place by the nuclear superpowers since 1992 (North Korea has tested its warheads more recently).

“The Trump administration would have a difficult time telling India, Pakistan and even Iran not to test nuclear devices if they resume such testing. Having created the nuclear norm against nuclear warhead testing, to start again now would be a deeply retrograde step,” he cautioned.

Mr Trump’s threat came just ahead of his summit with Chinese leader Xi Jinping. The Chinese Foreign Ministry urged Washington to “earnestly fulfil its obligations under the Comprehensive Nuclear Test Ban Treaty and honour its commitment to suspend nuclear testing.”