A Doomsday Clock, which symbolises the current threat of global annihilation, is expected to be moved closer to midnight by scientists.
The countdown was established in 1947 by a group of experts who were working on the Manhattan Project to design and build the first atomic bomb.
They wanted a simple way of demonstrating the danger to Earth and humanity posed by nuclear war.
The clock is currently running at three minutes to midnight, where 00.00 represents the end of humanity.
But the Bulletin of the Atomic Scientists is expected to move it forward by one minute on Thursday, the closest it has ever been to the apocalypse since 1953 when the US took the decision to upgrade its nuclear arsenal with the hydrogen bomb.
The Doomsday Clock now not only takes into account the likelihood of nuclear Armageddon but also other emerging threats, such as climate change and advances in biotechnology and artificial intelligence.
Last month the Bulletin dropped a strong hint that Doomsday was about to edge nearer.
In a statement the scientists said: "Tensions between the United States and Russia that remain at levels reminiscent of the Cold War, the danger posed by climate change, and nuclear proliferation concerns - including the recent North Korean nuclear test - are the main factors influencing the decision about any adjustment that may be made to the Doomsday Clock."
On Sunday it posted an article on its website warning that "terrorism involving nuclear or radiological materials remains one of the gravest threats to humanity and to global stability".
The scientists also warned of "accidental, unauthorised, or inadvertent nuclear exchange between the United States and Russia", saying that the two countries had 800 warheads on high alert, ready to launch.
On Thursday the Bulletin will announce the new "time" in an event to be streamed live at 3.30pm GMT (midday NZST).
The clock was last moved in 2015, when the scientists took it two minutes forward, so that it currently reads three minutes to midnight.
That sent a message that the Earth was closer to oblivion than any time since the early days of hydrogen bomb testing and 1984, when US-Soviet relations reached "their iciest point in decades".
Last year the clock's hands, which have moved forwards and backwards in different years over the past decades, remained unchanged.
A statement accompanying the 2016 Doomsday Clock decision read: "Three minutes (to midnight) is too close. Far too close.
"We, the members of the Science and Security Board of the Bulletin of the Atomic Scientists, want to be clear about our decision not to move the hands of the Doomsday Clock in 2016. That decision is not good news, but an expression of dismay that world leaders fail to focus their efforts and the world's attention on reducing the extreme danger posed by nuclear weapons and climate change.
"When we call these dangers existential, that is exactly what we mean: They threaten the very existence of civilisation and therefore should be the first order of business for leaders who care about their constituents and their countries."
The clock was originally set to seven minutes to midnight and the world reached its safest point in 1991, when it read 17 minutes to midnight as the Cold War officially ended and The Strategic Arms Reduction Treaty greatly reduced the number of strategic nuclear weapons deployed by the US and Russia.