Comments by US President Donald Trump and a "darkening global security landscape" have made the world less safe, the Bulletin of the Atomic Scientists warned Thursday, moving its symbolic "Doomsday Clock" 30 seconds closer to midnight.
The clock -- which serves as a metaphor for how close humanity is to destroying the planet -- was last changed in 2015, from five to three minutes to midnight.
It is now set at two and a half minutes to midnight.
The decision to move the clock or not is led by a group of scientists and intellectuals, including 15 Nobel laureates.
The minute-hand on the clock was moved amid concerns about "a rise in strident nationalism worldwide, President Donald Trump's comments on nuclear arms and climate issues, a darkening global security landscape that is colored by increasingly sophisticated technology, and a growing disregard for scientific expertise," the group said in a statement.
The Doomsday Clock was created in 1947. It has changed 19 times since then, ranging from two minutes to midnight in 1953 to 17 minutes before midnight in 1991.
"Never before has the Bulletin decided to advance the clock largely because of the statements of a single person," two scientists at the Bulletin, Lawrence Krauss and David Titley, said in an opinion piece published by The New York Times.
"But when that person is the new president of the United States, his words matter."