Global catastrophe could be just two-and-a-half minutes away, according to scientists behind the Doomsday Clock.
The new "time" was brought forward by 30 seconds, the clock's keepers announced from Washington DC yesterday.
The Bulletin Of The Atomic Scientists, an expert group formed in 1945, takes into account the likelihood of nuclear Armageddon as well as other emerging threats such as climate change and advances in biotechnology and artificial intelligence.
In a statement the Bulletin's executive director Rachel Bronson, said: "Today's complex global environment is in need of deliberate and considered policy responses.
"It is ever more important that senior leaders across the globe calm rather than stoke tensions that could lead to war, either by accident or miscalculation."
The world is now a more dangerous place than it was a year ago, the scientists said, referring directly to the election of President Donald Trump in the US and alleged Russian cyber-hacking during the campaign.
Mr Trump's comments on growing the US nuclear arsenal have been called "ill-considered" they said, as they expressed concern at his "troubling propensity to discount or outright reject expert advice" on global security.
The scientists also described his appointments to environmental roles as people who "dispute the basics of climate science".
They added: "In short, even though he has just now taken office, the president's intemperate statements, lack of openness to expert advice, and questionable cabinet nominations have already made a bad international security situation worse."
The closest the clock, symbolising the threat of apocalypse, has ever come to striking midnight was in 1953, when it was timed at two minutes to midnight.
In that year the US took the decision to upgrade its nuclear arsenal with the hydrogen bomb, "a weapon far more powerful than any atomic bomb".
In 2015 the clock was brought two minutes forward, taking it to three minutes to midnight. Last year it remained unchanged, but scientists warned this was still "far too close".
The Bulletin was founded by concerned US scientists involved in the Manhattan Project that developed the world's first nuclear weapons during World War II. In 1947 they established the Doomsday Clock to provide a simple way of demonstrating the danger to the Earth and humanity posed by nuclear war.