Korea War Would Be 'Catastrophic,' Diplomacy Bearing Fruit: US's Mattis

WATCH LIVE: State Department expected to address North Korean threats in news briefing

WATCH LIVE: State Department expected to address North Korean threats in news briefing

Deviating from the tone of President Trump, who said the USA would unleash "fire and fury" upon North Korea, Mattis stressed that the route forward would be diplomatic, and he repeated the importance of the unanimous 15-1 United Nations Security Council vote to impose economic sanctions on North Korea.

Seoul's Joint Chiefs of Staff spokesman Roh Jae-cheon said Thursday that the US and South Korean militaries are prepared to "immediately and sternly punish" any kind of provocation by North Korea, but didn't elaborate on how the allies are preparing. And I want to stay right there right now.

"The tragedy of war is well enough known", Mattis said, responding to a question about the human toll of a nuclear confrontation between the DPRK and the U.S. "It does not need another characterization beyond the fact that it would be catastrophic".

A day earlier, President Trump threatened North Korea with "fire and fury" in response to reports of a new milestone in the country's nuclear quest.

The President's comments on Tuesday have been the backdrop to a week of growing tensions on the Korean peninsula.

North Korea announced that military leaders are planning to launch four intermediate-range Hwasong-12 missiles only 25 miles off the coast of Guam, a USA territory in the Pacific Ocean.

Mattis also noted that the U.S.is also ready for a military conflict if it comes to that.

If carried out, it would be the North's most provocative missile launch to date.

Tillerson's more moderate line, however, was seemingly dismissed by Deputy Assistant to the President Sebastian Gorka in an interview with BBC on Thursday.

A number of US allies, including Australia and Japan, have said that they're prepared to stand with Trump and will take military action against North Korea if Jong Un launches an attack against Guam, according to Fox News.