President Trump on Wednesday ratcheted up his rhetoric against North Korea, pointing to the strength of the U.S. nuclear arsenal one day after warning Pyongyang of "fire and fury" if it continued its threats.

Trump said in a series of tweets that he hoped that the "power" of the U.S. nuclear arsenal would never have to be used.

He added that "there will never be a time that we are not the most powerful nation in the world."

My first order as President was to renovate and modernize our nuclear arsenal. It is now far stronger and more powerful than ever before.... — Donald J. Trump (@realDonaldTrump) August 9, 2017

...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! — Donald J. Trump (@realDonaldTrump) August 9, 2017

Trump's tweets come less than a day after he made a dire warning to North Korea's leader, Kim Jong Un.

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"He has been very threatening beyond a normal state, and as I said they will be met with fire, fury and frankly power, the likes of which this world has never seen before,” Trump said at his golf club in Bedminster, N.J.

Those provocative comments followed a report that North Korea crossed a major threshold in its quest to become a nuclear power by successfully producing a miniaturized nuclear warhead that can fit onto a missile.

The White House later on Wednesday said that the tone of Trump's statement was discussed in advance though the words were picked off the cuff by the president.

“General Kelly and others on the NSC team were well aware of the tone of the statement of the president prior to delivery," said White House press secretary Sarah Huckabee Sanders. "The words were his own. The tone and strength of the message were discussed beforehand."

She said Trump's advisers "were clear the president was going to respond to North Korea’s threats following the sanctions with a strong message in no uncertain terms.”

After Trump's comments, North Korea raised the possibility of missile strikes on Guam. The North's state-run media warned Pyongyang would "turn the U.S. mainland into the theater of nuclear war" if it saw signs of a possible American attack.

But amid Trump's rhetoric, Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE on Wednesday urged Americans to remain calm and said he doesn't believe there is "any imminent threat" from North Korea.

“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,” Tillerson said in Guam. “I think the president just wanted to be clear to the North Korean regime on the U.S.'s unquestionable ability to defend itself, will defend itself and its allies.”

Guam's top homeland security official also said there is little to no chance a North Korea missile could make it past the island's defenses.

George Charfauros said Guam is protected by the Terminal High Altitude Area Defense missile system, which is permanently stationed at Andersen Air Force Base on the island.

"There’s .00001 percent chance of that missile getting through that layer," Charfauros told reporters at a news conference, according to Pacific Daily News.

Guam's governor echoed the sentiment, telling residents it is "not the time to panic."

“There have been many statements out there that have been made by a very bellicose leader, but at this point there’s been no change in the security situation here on Guam," Eddie Calvo said.

While officials sought to downplay the threat, a Trump aide on Wednesday said that North Korea should not test the president.

Sebastian Gorka touted the strength of the U.S. during an interview on Fox News and cautioned North Korea against testing the president.

“We are not just a superpower. We were a superpower. We are now a hyperpower," Gorka said on "Fox & Friends."

"Nobody in the world, especially not North Korea, comes close to challenging our military capabilities, whether they’re conventional, whether they’re nuclear, or whether they’re special forces. So the message is very clear: Don’t test this White House.”

Earlier this year, the Pentagon announced it had started a review of the U.S. nuclear posture, which Trump ordered in a January executive action on military readiness.

The January memo called for a review “to ensure that the United States nuclear deterrent is modern, robust, flexible, resilient, ready and appropriately tailored to deter 21st-century threats and reassure our allies.”

The last time the military conducted a nuclear posture review was in 2010.

Last month, 22 Senate Democrats called for a "transparent and inclusive" process in the Trump administration's ongoing review of the U.S. nuclear weapons policy.

This report was updated at 2:05 p.m.

Jordan Fabian contributed.