After days of fiery rhetoric from both the USA and North Korea, Mr Mattis said war would be "catastrophic" and that diplomacy was gaining results.
The US Defense Department is hoping for a diplomatic solution that would halt North Korea's quest for a nuclear intercontinental ballistic missile (ICBM) capable of reaching the United States, but has military solutions ready if ordered to act, Secretary of Defense Jim Mattis said in a press briefing on Thursday. On Thursday, Mattis went on to say the Trump administration is "prioritizing the threat" but also looking at "how to deal with it in a diplomatically effective manner".
President Donald Trump again stepped up the rhetoric against North Korea on Thursday, saying an earlier threat to unleash "fire and fury" on Pyongyang if it launched an attack was not tough enough.
Mattis praised the efforts of United Nations Ambassador Nikki Haley that resulted in a U.N. Security Council resolution condemning North Korea's actions.
North Korea "should cease any consideration of actions that would lead to the end of its regime and the destruction of its people", Mattis said in an August 9 statement.
Analysts say the new sanctions could cut off roughly one-third of North Korea's estimated $3 billion in annual exports and put a huge dent in the funding Pyongyang needs for its weapons and nuclear programs.
"My first order as president was to renovate and modernize our nuclear arsenal". "Hopefully we will never have to use this power, but there will never be a time that we are not the most powerful nation in the world!"
'The current situation on the Korean Peninsula is highly complicated and sensitive.
"I think what the president was just reaffirming is that the United States has the capability to fully defend itself from any attack, and our allies, and we will do so", Tillerson said.
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.
"I was not elected, the American people elected the president", he said.