Donald Trump is ill-informed and living in a "cowboy world" when it comes to the nuclear threat from North Korea, a prominent activist has said.
Seasoned peace campaigner Bruce Kent also said he thinks Britain is "uniquely placed" to become the first nuclear power to "come off the fence".
During a period of heightened nuclear tensions arising from North Korea’s military tests, the vice president of the Campaign for Nuclear Disarmament (CND) said no one wins in nuclear war.
"It is a very dangerous time because a man like Trump really is not sufficiently informed to know what he is dealing with," the 88-year-old told the Press Association.
"He is still living in a kind of cowboy world, where the one with the bigger gun somehow wins. Well nobody wins with a nuclear war - there is no winning.
"We have had precarious times before, like the Cuban crisis, but this is quite a dangerous one - granted his volatile method of talking and thinking."
Mr Kent said it is a possibility that the US president could get "into a paddy and press the button", adding that "we shouldn’t have to take that risk".
But he stressed that he hopes there are enough people "with independent minds" to stop him if the situation arose.
Becoming involved with the CND in 1960, the former Roman Catholic priest of 35 years said the amount the Government spends on the Trident nuclear deterrent is a "gross waste of money".
He said of the plans to renew Trident: "They always talk about it as if it was just the building of the things. But if you add the building and the running of them it is something like £300 billion.
"It could be spent on housing or hospitals, or social services, or overseas aid - that money does not get challenged."
Mr Kent said the UK does not have an independent nuclear weapon, and that the country depends entirely on the Americans to supply the missiles.
"We are actually in a special position. If America or Trump said no more missiles for Britain, in six months we would no longer have a nuclear arsenal," he said.
"We would have the warheads, but we wouldn’t have anywhere to put them. We are well placed to be the first nuclear power to come off the fence."
In recent months Kim Jong Un’s regime has conducted several increasingly sophisticated nuclear tests, and has expanded its missile programme to include weapons allegedly capable of striking parts of the US.
Mr Trump has ridiculed Mr Kim as Rocket Man and has warned North Korea he will take all measures needed to stop the programme.
Asked if he thinks North Korea is a particular threat, Mr Kent said: "I think North Korea has nuclear weapons because of the world it lives in.
"It is looking out at the American fleet, it is looking at nuclear weapons pointed at it and it thinks to itself, just like Mrs May probably, that it is safer to have nuclear than to not have them.
"I think it is more dangerous for everybody.
"The answer to the North Korea problem is to get rid of American nuclear weapons from that area and de-target North Korea - not to encourage them to copy us.
"If nuclear weapons provide security there is no common sense in saying that other countries should not have them."
Mr Kent was speaking as supporters of CND, Medact and the International Campaign to Abolish Nuclear Weapons (ICAN) gathered outside the Ministry of Defence in London on Saturday.
ICAN won this year’s Nobel Peace Prize for its "work to draw attention to the catastrophic humanitarian consequences of any use of nuclear weapons and for its ground-breaking efforts to achieve a treaty-based prohibition of such weapons".
Ahead of ICAN receiving the award on Sunday the three groups staged their own ceremony which included the presentation of a handmade Nobel Peace Prize coin and speeches.
They also called on the Government to sign up to the newly approved UN treaty that bans nuclear weapons, and staged a "die in" - where the 25 activists who attended lay sprawled on the steps of the MoD to highlight the human cost of nuclear war.
Mr Kent described the Nobel Peace Prize being awarded to ICAN as "very significant".