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President Donald Trump on Friday warned North Korea's leader that he "will not get away with" it if he does anything against the U.S. or its allies.

"If he utters one threat in the form of an overt threat — which by the way he's been uttering for years, and his family has been uttering for years — or if he does anything with respect to Guam, or American territory or an American ally, he will truly regret it and he will regret it fast," Trump said of North Korean leader Kim Jong Un.

Speaking to reporters later after meeting with Secretary of State Rex Tillerson, U.N. Ambassador Nikki Haley and National Security Adviser H.R. McMaster, the president said he planned to talk to Chinese President Xi Jinping on Friday evening, noting that the two countries have been working "very closely" on the North Korea issue.

Trump also previewed that his administration was considering "very strong" additional sanctions on North Korea — "as strong as they can get," he added — but he did not offer any details.

The president said the only reason anyone was criticizing his handling of North Korea was because he was the one in charge.

"My critics are only saying that because it's me," Trump told reporters at his Bedminster, N.J., golf resort. "If somebody else uttered same words I did, they'd say what a wonderful statement."

He added, "Tens of millions in this country so happy with what I'm saying — finally we have president sticking up for our nation and for our friends and allies — and this man will not get away with what he's doing, believe me."

Earlier in the day, the president echoed similar sentiments.

"Military solutions are now fully in place, locked and loaded, should North Korea act unwisely," Trump tweeted Friday morning. "Hopefully Kim Jong Un will find another path!"

Moments later, he retweeted a message from the U.S. Pacific Command’s official Twitter account, stating that "#USAF B-1B Lancer #bombers on Guam stand ready to fulfill USFK’s #FightTonight mission if called upon to do so."

Military solutions are now fully in place,locked and loaded,should North Korea act unwisely. Hopefully Kim Jong Un will find another path! — Donald J. Trump (@realDonaldTrump) August 11, 2017

The U.S. military in the region surrounding the Korean Peninsula always remains prepared with both defensive and offensive capabilities, should North Korea launch an attack. "Ready to fight tonight," is their motto.

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Hours earlier, North Korea’s state-run KCNA news agency slammed the White House as “warmongers” who "are unaware of the fact that even a single shell dropped on the Korean Peninsula might lead to the outbreak of a new world war, a thermonuclear war."

"We consider the U.S. no more than a lump which we can beat to a jelly any time," Pyongyang said in its statement.

Trump said he would not respond until he heard such statements from Kim himself. "Let me hear Kim Jong-un say it," the president said, adding that the North Korean leader "hasn’t been saying much for the last three days."

Trump's latest tweets also came not long after a Chinese state-run newspaper said China should remain neutral if North Korea launches an attack that threatens the United States, sounding a warning for Pyongyang over its plans to fire missiles near the U.S. Pacific territory of Guam.

The comments from the influential Global Times came after Trump stepped up his rhetoric on Thursday against North Korea, saying his earlier threat to unleash "fire and fury" on Pyongyang if it launched an attack may not have been tough enough.

Trump also told reporters he would hold a "big press conference" Monday, but did not reveal the purpose.

China, North Korea's most important ally and trading partner, has reiterated calls for calm during the current crisis. Beijing has expressed frustration with both Pyongyang's repeated nuclear and missile tests and with behavior from South Korea and the U.S., such as military drills, that it sees as increasing tensions.

"China should also make clear that if North Korea launches missiles that threaten U.S. soil first and the U.S. retaliates, China will stay neutral," the Global Times, which is widely read but does not represent government policy, said in an editorial.

"If the U.S. and South Korea carry out strikes and try to overthrow the North Korean regime and change the political pattern of the Korean Peninsula, China will prevent them from doing so," it said.

The Kremlin weighed in on Friday, too, as Russian Foreign Minister Sergey Lavrov said the rhetoric from Washington and Pyongyang was "going over the top."

Trump said earlier this week Kim was not going to get away with his "horrific" comments and disrespecting America.

"Let's see what he does with Guam. He does something in Guam, it will be an event the likes of which nobody's seen before, what will happen in North Korea," Trump told reporters on Thursday.

He also said his previous promise of "fire and fury" in response to threats from North Korea may have not gone far enough, vowing "trouble" for the country if its actions don't change. "If anything, maybe that statement [about "fire and fury"] wasn’t tough enough," Trump said Thursday.

Shortly after Trump spoke Thursday, U.S. Defense Secretary James Mattis told reporters the United States still preferred a diplomatic approach to the North Korean threat and that a war would be "catastrophic."

Even as the war of words between the U.S and North Korean leaders builds, a steady push for a diplomatic solution has been happening both in front and behind the scenes.

Although the two nations do not have formal diplomatic relations, a back channel used by previous administrations through the United Nations remains open. The news was first reported by the Associated Press.

“They know how to reach us,” Deputy Assistant Secretary for Southeast Asia W. Patrick Murphy told reporters Friday.

Starting in February of this year, U.S. Special Envoy for North Korea, Joseph Yun and a senior North Korean diplomat for the United Nations, Kim Song Il, have been holding secret negotiations, focused on securing the release of American Otto Warmbier and other detained Americans but also discussing other aspects of the U.S. North Korean relationship.

“It's a channel we've used often to set up other negotiations with the North Koreans,” former CIA acting director and deputy director John McLaughlin told NBC News. “I don't think it's a time for escalating war of words here, playing chicken with them. I think Mattis has this right: get it in diplomatic channels, start to move it back, look for face-saving ways out and there's nothing to be gained by anyone in a confrontation at this point."

Secretary of State Rex Tillerson has said the U.S. would like to sit down for formal talks with North Korea if they meet certain conditions but what those conditions are is not entirely clear.

“We'll know when we see it,” Tillerson said Monday. “The best signal that North Korea could give us that they are prepared to talk would be to stop these missile launches.”

Murphy later played down the possibility of diplomacy with Pyongyang.

"Now is not the opportunity for dialogue," Murphy said.

"Dialogue is not something to be negotiated. Standing down on the pursuit of dangerous missiles and nuclear programs in defiance of the international community, in defiance of the Security Council resolutions is what is at stake here," he said.

Trump declined on Friday to comment on the success of U.S. diplomatic back channels with North Korea, instead saying his administration's handling of the issue will "either be very, very successful quickly or we're gonna be very, very successful in a different way, quickly."

Adam Edelman reported from New York. Ali Vitali, Abigail Williams and Courtney Kube reported from Washington, D.C.