President Donald Trump issued an extraordinary threat to North Korea on Tuesday warning "North Korea best not make any more threats to the United States. They will be met with fire and fury like the world has never seen. They will be met with fire, fury and frankly power the likes of which the world has never seen."
Trump's harsh words come as US intelligence analysts have assessed that North Korea has produced a miniaturized nuclear warhead, according to multiple sources familiar with the analysis of North Korea's missile and nuclear program.
It is not believed that the capability has been tested, according to the sources.
This is not a consensus view from the entire intelligence community, one US official said. The Washington Post, which was first to publish details, reported that it was the analysis of the Defense Intelligence Agency.
The US official familiar with the analysis of North Korea's missile and nuclear program says, in reference to North Korea's leader Kim Jong Un's boasts about the program, "we have to take him at his word and we need to be prepared to deal with it."
This official said the 'assessment" is continuing to be refined and updated as more intelligence is collected.
The officials all note that the evidence shows North Korea is making progress and the question is more about when not if North Korea is capable of launching a nuclear capable missile.
Referring to Kim Jong Un, the official said this report needs to be taken seriously as "we've seen him moving forward" on the program with no indication he is turning back.
US military commanders have long planned on the assumption that North Korea has a warhead.
In 2014, then-commander of US Forces Korea Gen. Curtis Scaparrotti said he believed that they had the capability to miniaturize a warhead.
"I believe they have the capability to have miniaturized a device at this point, and they have the technology to potentially actually deliver what they say they have," Scaparrotti said at the time.
The Washington Post first reported details of the assessment on Tuesday just hours after North Korea threatened 'physical action' in response to punitive sanctions unanimously passed by the United Nations Security Council over the weekend.
CNN has previously reported that US intelligence estimates Pyongyang may have the capacity to deliver a nuclear weapon to the US mainland by early next year and its missile program showed significant progress during two intercontinental ballistic missile tests in July.
"Assuming everything is true, including that intelligence assessment both existing and everything being accurate, there are still important unknowns," Republican Rep. Lee Zeldin told CNN's Wolf Blitzer, noting that questions still linger about whether a possible North Korean warhead could survive re-entry from the earth's upper atmosphere.
However, Zeldin also said that reporting of the development "increases the urgency of the time sensitivity" of efforts being taken by the US and its international partners to address North Korea's missile and nuclear programs diplomatically.
Earlier on Tuesday, President Trump was quick to highlight his administration's success in leading the UN Security Council to unanimously pass sanctions on North Korea.
"After many years of failure,countries are coming together to finally address the dangers posed by North Korea. We must be tough & decisive!" Trump wrote in a tweet on Tuesday morning.
But reports that North Korea has taken another big step forward in realizing its nuclear ambitions will likely only escalate an already tense situation after the latest chapter of rhetorical chest-thumping.
US Ambassador to the United Nations Nikki Haley called newly approved sanctions on North Korea "a gut punch" and warned of possible military action should the regime continue its aggressive actions.
Those military options include launching a "preventative war" against North Korea, according to White House national security adviser H.R. McMaster.
"If they had nuclear weapons that can threaten the United States, it's intolerable from the President's perspective. Of course, we have to provide all options to do that, and that includes a military option," McMaster said in an interview with MSNBC on Saturday.
North Korean Foreign Minister Ri Yong Ho said Pyongyang "will, under no circumstances, put the nukes and ballistic rockets on the negotiating table," and would "teach the US a severe lesson" if it used military force against North Korea.
North Korea was estimated to have between 13 and 30 nuclear weapons at the end of 2016, according to the Institute for Science and International Security -- noting that North Korea keeps secret the number of nuclear weapons that it has built, and there is little, if any, reliable public information about this value.