A panel of scientists and scholars have moved ahead by half a minute the symbolic Doomsday Clock, saying the world is at its closest to annihilation since the height of the Cold War due to world leaders' poor response to threats of nuclear war and climate change.

It was the second occasion the timepiece, created by the Bulletin of the Atomic Scientists as an indicator of the world's susceptibility to cataclysm, was moved forward since the 2016 election of US president Donald Trump.

At two minutes to midnight, the clock is at its closest to the end of humanity since 1953, due to dangers of a nuclear holocaust from North Korea's weapons program, US Russian entanglements, South China Sea tensions, and other factors, the Chicago-based group said in a statement.

Bulletin officials Lawrence M. Krauss, a theoretical physicist, and Robert Rosner, an astrophysicist, wrote in an op-ed in the Washington Post that the situation was "dire".

"To call the world nuclear situation dire is to understate the danger - and its immediacy. North Korea's nuclear weapons program appeared to make remarkable progress in 2017, increasing risks for itself, other countries in the region and the United States."

The group said that "hyperbolic rhetoric and provocative actions on both sides have increased the possibility of nuclear war by accident or miscalculation".

Unchecked dangers linked to climate change were another factor scientists cited for moving the clock forward.

An overarching concern was what scientists described as the demise of diplomacy under the Trump administration.

"International diplomacy has been reduced to name-calling, giving it a surrealistic sense of unreality that makes the world security situation ever more threatening," they said.

In a September speech at the United Nations, Trump threatened to "totally destroy North Korea" to defend the United States or its allies, and referred to Kim by the new nickname he had just given the dictator on Twitter, saying: "Rocket Man is on a suicide mission for himself."

Kim responded with an arcane insult, declaring in an unusually direct and angry statement published by North Korea's official Korean Central News Agency: "I will surely and definitely tame the mentally deranged US dotard with fire."

Two months later, North Korea tested a new kind of intercontinental ballistic missile and declared that the entire US mainland is within reach. Experts calculated that the missile flew 10 times higher than the International Space Station and could theoretically reach Washington, DC.

Trump responded on Twitter, saying that his nuclear button was bigger and "my button works!"

Then there was the errant alert that went out to Hawaii residents and tourists earlier this month: "BALLISTIC MISSILE THREAT INBOUND TO HAWAII. SEEK IMMEDIATE SHELTER. THIS IS NOT A DRILL."

It all prompted an op-ed last month from Bulletin contributor Jeffrey Lewis: "This is how nuclear war with North Korea would unfold."

To rewind the clock, scientists recommended Trump refrain from provocative rhetoric regarding North Korea, the two countries open multiple communication channels and the world community seek a cessation of North Korea's nuclear weapon and ballistic missile tests.

The clock is symbolic, sitting at the intersection of art and science, and it has wavered between two and 17 minutes until doom since its inception in 1947.

When the clock was created in 1947, it was set at 7 minutes to midnight.

The Bulletin of the Atomic Scientists was founded by veterans of the Manhattan Project concerned about the consequences of their nuclear research.

One of them, nuclear physicist Alexander Langsdorf, was married to artist Martyl Langsdorf, who created the clock and set it at seven minutes to midnight, or 11:53, for the cover of the group's magazine. Her husband moved the time four minutes ahead in 1949.

The group helped develop the United States' first atomic weapons. Its Science and Security Board, which decides on the clock's hands, which includes 15 Nobel laureates.

Last year the clock's hands were pushed forward 30 seconds to their second closest point to midnight - two minutes and 30 seconds - after Trump's statements regarding the proliferation of nuclear weapons and the prospect of actually using them.

In 2016, the clock remained unmoved, its hands staying at three minutes to midnight.

The clock is displayed on the group's website.