Secretary of State Rex Tillerson has urged calm and said Americans should have "no concerns" after North Korea and President Donald Trump traded fiery threats.
He said he does not believe there is "any imminent threat", and "Americans should sleep well at night".
Mr Tillerson sought to explain the thinking behind President Trump's warning to Pyongyang that it would be "met with fire and fury like the world has never seen" if it made more threats to the United States.
Mr Tillerson said President Trump was trying to send a strong and clear message to North Korea's leader so that there would not be "any miscalculation".
"What the president is doing is sending a strong message to North Korea in language that Kim Jong Un can understand, because he doesn't seem to understand diplomatic language," Mr Tillerson said.
"I think the president just wanted to be clear to the North Korean regime on the US unquestionable ability to defend itself, will defend itself and its allies."
He said North Korea's escalating threats showed it was feeling the pressure from a successful US strategy.
Mr Tillerson downplayed any speculation that the alarming developments suggested the US was moving closer to a military option to dealing with the crisis over the North's nuclear and ballistic missile programmes.
"Nothing that I have seen and nothing that I know of would indicate that the situation has dramatically changed in the last 24 hours," Mr Tillerson said.
Mr Tillerson spoke to reporters aboard his plane as he returned from Malaysia to Washington, stopping along the way in Guam.
Hours earlier, North Korea's army had said in a statement it was exploring plans for attacking the tiny US territory, which houses US military bases and is a common refuelling stop for US government aircraft crossing the Pacific Ocean.
Mr Tillerson said he never considered re-routing his trip from Malaysia so as to avoid stopping in Guam.
Though he insisted there was no imminent threat, he noted that even if there were, "the North Korean missile capability can point in many directions, so Guam is not the only place that would be under threat".
The comments put Mr Tillerson once again in the role of translating the president's aggressive rhetoric into more diplomatic terms, and of working to minimise the chances of a public panic.
Though it is extremely unlikely the North would risk annihilation by pre-emptively attacking American citizens, the escalating rhetoric has heightened concern that a miscalculation could spiral out of control and lead to military conflict - a concern that residents of Guam said they felt particularly acutely.
Mr Tillerson, who spent the past days in Asia working the North Korea conflict, said he did not believe a new diplomatic strategy was needed.
To the contrary, he said the latest threat from the North suggested the current strategy was working.
After months of frustration over China's reluctance to pressure Pyongyang economically, the US on Saturday secured a unanimous UN Security Council vote to authorise sweeping new sanctions that target one-third of the North's exports.
"The pressure is starting to show," Mr Tillerson said.
"I think that's why the rhetoric coming out of Pyongyang is beginning to become louder and more threatening. Whether we've got them backed into a corner or not is difficult to say, but diplomatically, you never like to have someone in a corner without a way for them to get out."
To that end, Mr Tillerson said there was still an off-ramp available to Pyongyang: A return to negotiations with the US, a step that Mr Tillerson has previously said can happen only if Kim Jong Un's government gives up its nuclear aspirations, starting with an extended pause in missile tests.
"Talks," Mr Tillerson said when asked if North Korea had a way out.
"Talks, with the right expectation of what those talks will be about."
President Donald Trump later said that the United States' nuclear arsenal is "far stronger and more powerful than ever before".
President Trump tweeted: "My first order as President was to renovate and modernise our nuclear arsenal. It is now far stronger and more powerful than ever before...."
The tweet came as the president traded escalating threats with North Korea.