US Defense Secretary James Mattis issued a dramatic warning to North Korea to "cease any consideration of actions that would lead to the end of its regime and destruction of its people" on Wednesday - just one day after President Donald Trump warned that the US could unleash "fire and fury" on Pyongyang.
"The DPRK must choose to stop isolating itself and stand down its pursuit of nuclear weapons", Mattis said in a statement, using an acronym for North Korea.
Mattis, rather than threatening to strike if North Korea continues to make threats, said that North Korea "would lose any arms race of conflict it initiates", which adheres to a long-standing policy of attempting to deter North Korea with the promise of a swift, overwhelming response to any attack.
"They will be met with fire and fury like the world has never seen", Trump said.
The warning came soon after The Washington Post reported the North has successfully miniaturized a nuclear warhead to fit atop its missiles.
"We always maintain a high state of readiness and have the capabilities to counter any threat, to include those from North Korea", Lt. Col. Christopher Logan, a Pentagon spokesman, told CBN News.
It has not conducted a nuclear test since September 2016. He said the USA nuclear arsenal is the most powerful it's ever been under his leadership.
Trump's unexpected remarks prompted North Korea to respond that it was considering plans for a missile strike on the US Pacific territory of Guam.
Mattis has warned that North Korea now poses the most urgent threat to USA peace and security, but also that any war with Pyongyang would include "probably the worst kind of fighting in most people's lifetime", citing the threat posed by hundreds of North Korean rocket launchers and artillery pieces aimed at Seoul.
"There's obviously growing concern, and that concern is fueled when the president of the United States deliberately uses language that escalates sort of the war of words and I think, unfortunately, matches the tone and tenor of North Korean officials", Kildee said. On Saturday, for example, members of the U.N. Security Council approved new economic sanctions on the regime.
President Trump on Wednesday declared the USA nuclear arsenal "far stronger and more powerful than ever before" even as his top diplomat was working to calm the North Korea crisis and insisting there wasn't "any imminent threat".
Guam is a US territory in the western Pacific that is home to a key Air Force base. Democratic leaders criticised Trump for his statement on North Korea.
These are some of strongest comments Mattis has made on North Korea.
Tens of thousands of USA troops remain stationed in South Korea and in nearby Japan, the only country to have been attacked with nuclear weapons.