The Labour leader warned you “cannot play fast and loose with nuclear weapons”, adding that Britain had a role to play in bringing the two leaders “back from the brink”.

The comments came as the US President risked further tensions by tweeting: “Military solutions are now fully in place, locked and loaded, should North Korea act unwisely. Hopefully Kim Jong-un will find another path!”

The rogue state has said it plans to fire missiles towards a US nuclear base in Guam, having developed – US intelligence officials believe – a nuclear warhead small enough to fit inside its missiles.

Mr Trump has said any such threats would be “met with fire and fury like the world has never seen”, later suggesting that the warning “may not be tough enough”.

Speaking in Bristol, Mr Corbyn said: “We cannot play fast and loose with nuclear weapons and nuclear threats because do you know what – a nuclear explosion doesn’t stop at national borders, it doesn’t stop at the vicinity where the bomb drops.”

The Labour leader, a long time anti-war campaigner, said the result of a nuclear strike would go on for decades, adding: “I ask them both, calm down.

“There are phone calls that could be made, there’s discussions that could be held. Surely, in the interests of sanity and safety over the whole world, do it.”

Mr Corbyn said Britain and other nations with nuclear weapons also had a role to play in reducing the tensions.

“All the five declared nuclear weapons states, which includes the United States, Russia and China, as well as Britain and France, need to get on board on this to bring North Korea back from the brink, bring Donald Trump back from the brink, and support the NPT [the treaty on the non-proliferation of nuclear weapons] and support the UN’s efforts to make nuclear weapons illegal worldwide,” he said.

Meanwhile, a Pentagon spokesman said a joint military exercise between the US and South Korea was expected to start, as planned, on 21 August.

Russia accused both the US and North Korea of inflammatory language and warned the risks of a conflict were very high. Foreign Minister Sergey Lavrov put forward a peace plan under which the communist state would freeze missile tests in return for the military exercise being called off.

Earlier, a Government source denied a claim that the US has requested Britain’s help to find North Korea’s nuclear weapon sites and prepare for military strikes.

The report, that the RAF has been asked to join an international spying operation to pinpoint nuclear locations and artillery batteries, was “flat out wrong”, The Independent was told.

Theresa May, who is still on holiday, is yet to comment on the growing crisis between North Korea and the US.

But her deputy, Damian Green, appeared to criticise President Trump’s threat to unleash “fire and fury” on North Korea, raising the threat of nuclear war.