The United States is preparing to put nuclear bomber planes on 24-hour alert for the first time since the Cold War, a senior Air Force official has said.
A fleet of B-52s laden with nuclear weapons could soon be readied to launch within a day's notice amid growing tensions with North Korea.
General David Goldfein, Air Force Chief of Staff, said US military leaders were being forced to adapt to "the reality of the global situation we find ourselves in".
“The world is a dangerous place and we’ve got folks that are talking openly about use of nuclear weapons,” he told national security news website Defense One.
Pyongyang has made rapid progress on its nuclear weapons and intercontinental missile programmes this year, while North Korean leader Kim Jong-un and US President Donald Trump have exchanged threats of war.
Mr Goldfein stressed an order had not yet been given to put nuclear bombers on alert, but said preparations were underway in anticipation that it might be.
“This is yet one more step in ensuring that we’re prepared,” he said during a tour of Air Force bases home to nuclear bombers. "I look at it more as not planning for any specific event, but more for the reality of the global situation we find ourselves in and how we ensure we’re prepared going forward.”
He added: “It’s no longer a bipolar world where it’s just us and the Soviet Union. We’ve got other players out there who have nuclear capability. It’s never been more important to make sure that we get this mission right.”
Renovations are reportedly currently being made to Barksdale Air Force base, home to the 2nd Bomb Wing and Air Force Global Strike Command, which oversees the US nuclear forces.
Beds are being installed for more than 100 crew members - enough to man bombers that would be positioned on nine concrete alert pads.
Mr Goldfein's comments came after the director of the CIA said North Korea was months away from perfecting its nuclear weapons.
Mike Pompeo told a national security forum Pyongyang was “close enough now in their capabilities that from a US policy perspective we ought to behave as if we are on the cusp of them achieving” their objective of being able to strike the US.
On Sunday, Mr Trump said the US was "prepared for anything" over the North Korea nuclear crisis.
"We'll see what happens... We are so prepared, like you wouldn't believe," he told Fox News.
Last week North Korea threatened to launch an “unimaginable” strike on the US, accusing the Trump administration and its South Korean “puppet” allies of seeking to “ignite a war on the Korean peninsula at any cost”.
In the latest in a series of dramatic statements, Pyongyang predicted “imminent catastrophic disaster” in the region.
A Japanese official said Prime Minister Shinzo Abe and the US President Donald Trump had agreed to work together to raise pressure on North Korea after the premier's ruling coalition won a sizeable majority in the country's election on Sunday.
Yasutoshi Nishimura, a deputy chief cabinet secretary, said Mr Abe and Mr Trump were planning to play golf together on November 5, when the President makes his first visit to Japan.
