"While our State Department is making every effort to resolve this global threat through diplomatic means, it must be noted that the combined allied militaries now possess the most precise, rehearsed and robust defensive and offensive capabilities on Earth", Mattis said.
Speaking in California later Thursday, Mattis praised the diplomatic leadership of Tillerson and U.S. Ambassador to the UN Nikki Haley, as well as a unanimous vote by the UN Security Council to impose fresh sanctions on North Korea.
The North was responding to Trump's threat in a statement from its military carried by state-run news agency KCNA.
Pyongyang has been louder in its complaints against a new and tough round of sanctions imposed by the United Nations, with strong U.S. backing, and Washington's use of Guam as a staging ground for its stealth bombers, which could be used to attack North Korea and are a particularly sore point with the ruling regime in Pyongyang.
According to two U.S. military sources which spoke to NBC, U.S. intelligence has identified at least two dozen targets in the DPRK, which they say consist of missile launch sites, testing grounds, storage facilities and support equipment.
Turnbull says: "The United States knows as we know and as Donald Trump reaffirmed. that America stands by its allies including Australia of course and we stand with the United States".
In a lengthy exchange with reporters at his Bedminster golf resort, he said past administrations had not done enough to take on North Korea and that it was time a president "stuck up for the country".
United Nations spokesman Stephane Dujarric says Guterres "welcomes all initiatives that will help de-escalate the tensions and a return to diplomacy".
"China should make clear that if North Korea launches missiles that threaten US territories and triggers USA retaliations, China will stay neutral".
On Thursday, U.S. and Japanese troops began an 18-day live fire exercise on the northern Japanese island of Hokkaido, which was to include rocket artillery drills and involve 3,500 troops.
And U.S. Defense Secretary James Mattis on Thursday appeared to downplay the possibility of armed conflict.
Japan and South Korea vowed a strong reaction if the North were to go through with the plan.
"North Korea has said it may attack Guam in retaliation".