With all 100 U.S. senators invited to a rare briefing on White House grounds Wednesday on North Korea, it’s hard to overstate how concerned officials are about the technological advancements out of Pyongyang.

While North Korea’s leader Kim Jong-un has a reputation for bizarre behavior, the nuclear arsenal and aspirations of the Republic are being taken seriously.

North Korea has conducted five nuclear tests in the past 11 years, the last several being the most destructive – and now they are threatening a sixth.

North Korea’s official Rodong Sinmun newspaper also said in a front-page editorial that its military is prepared "to bring to closure the history of U.S. scheming and nuclear blackmail.”

The editorial said, "There is no limit to the strike power of the People's Army armed with our style of cutting-edge military equipment including various precision and miniaturized nuclear weapons and submarine-launched ballistic missiles.”

It is that miniaturized nuclear weapon that is the biggest concern to the United States, and the rest of the world.

“They have expressed the intent to [miniaturize a nuclear weapon],” Thomas Karako, the director of the Missile Defense Project at the Center for Strategic and International Studies, told Fox News. “It raises the stakes and increases the risk of missile threats to the region and the U.S. homeland.”

North Korea would need that smaller nuclear weapon to deliver it long-distance. According to the New York Times, “As Dr. [Siegfried] Hecker, a man who has built his share of nuclear weapons, noted last week, any weapon that could travel that far would have to be 'smaller, lighter and surmount the additional difficulties of the stresses and temperatures' of a fiery re-entry into the atmosphere. By most estimates, that is four or five years away. Then again, many senior officials said the same four or five years ago.”

Secretary of State Rex Tillerson, Secretary of Defense Jim Mattis, Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford and Director of National Intelligence Dan Coats are expected to update senators on the North Korea situation Wednesday afternoon.

President Trump told a meeting of United Nations Security Council ambassadors on Monday they must be prepared to impose additional and stronger sanctions on North Korea. “This is a real threat to the world, whether we want to talk about it or not,” Trump said.

Obtaining reliable intelligence on North Korea has always been difficult. Kim Jong-un rules the country with an iron fist. The nation is so cut off from the world that is has been dubbed the ‘hermit kingdom.’

In March of last year, North Korea released photographs of Kim Jong-un inspecting what appears to be a miniaturized implosion device, but that photo op was met with skepticism. “No reason to believe that is true, or to disbelieve it. No reason to dismiss it or to panic,” Karako said. He added, “I think that our insight into these programs is relatively modest. I think the posture of our military is to assume the worst.”

This has the U.S., and the world, on high alert. The Global Times, a state-run Chinese newspaper, published an editorial on Tuesday stating, “The game of chicken between Washington and Pyongyang has come to a breaking point. If North Korea carries out a sixth nuclear test as expected, it is more likely than ever that the situation will cross the point of no return.”