President Donald Trump used his visits this week to China and South Korea to continue his aggressive stance toward North Korea and its leader Kim Jong-un over the country’s nuclear weapons program.

“This is a very different administration than the United States has had in the past,” Trump said to the North Korean government during a speech before the South Korean Assembly. “Do not underestimate us. And do not try us.”

Part of the justification for Trump’s more bellicose rhetoric is the notion that North Korea’s nuclear program represents a military threat not just to its neighbors like South Korea and Japan but to the United States itself. Just how legitimate are those claims?

To even begin to answer that, we need to think in terms of two separate issues: Whether North Korea can make a working nuclear warhead, and whether it can place that warhead on top of a missile capable of successfully reaching U.S. territory.

“Despite what some analysts believe, others say there is no definitive, publicly available proof that North Korea has a missile with the range to strike the continental United States, a miniaturized nuclear warhead to mate with it, and the shielding technology to make sure the warhead survives the heat and pressure of reentry to the atmosphere,” John Mecklin, the editor-in-chief of the Bulletin of Atomic Scientists, wrote in Reuters this September.

In assessing what North Korea’s nuclear strike capabilities actually are, we are fundamentally limited by all we don’t know, according to an analysis published in Mecklin’s publication this August. As such, skepticism is generally warranted when either North Korea or the United States make claims about the former’s nuclear program.

Kim Il Sung Square and Grand People's Study House in Pyongyang, North Korea, in 2015.

“At this time, no one outside of North Korea has solid information about the characteristics of North Korea’s nuclear weapons designs—especially about whether or not the weapons that have been tested are cumbersome laboratory devices or readily militarized designs that could be put into bombs or carried on ballistic missiles,” a trio of physicists write in the Bulletin. “This information is simply not available at this time.”

As the analysis explains, estimating the range of North Korea’s missiles relies on studying their flightpaths — which typically achieve high vertical altitudes but don’t travel very far horizontally — and extrapolating how far said missiles could reach if they had an almost entirely horizontal trajectory. Missile tests in July suggest North Korea has missiles that could reach as far as Anchorage, Alaska, or perhaps even Seattle, Washington.

That sounds scary, but there’s a pretty big caveat, according to the analysis in the Bulletin: The missile could only ever get that far if North Korea stripped it of any actual working warhead. Adding even the small weight of a warhead would likely limit the range of such a missile so that it couldn’t reach Alaska, let alone the lower 48.

“In reality, the North Korean rocket fired twice last month — the Hwasong-14 — is a “sub-level” ICBM that will not be able to deliver nuclear warheads to the continental United States,” the physicists write. “Our analysis shows that the current variant of the Hwasong-14 may not even be capable of delivering a first-generation nuclear warhead to Anchorage, Alaska, although such a possibility cannot be categorically ruled out. But even if North Korea is now capable of fabricating a relatively light-weight, ‘miniaturized’ atomic bomb that can survive the extreme reentry environments of long-range rocket delivery, it will, with certainty, not be able to deliver such an atomic bomb to the lower 48 states of the United States with the rocket tested on July 3 and July 28.”

That still leaves Hawaii and the American territory of Guam, which North Korea publicly threatened in August before backtracking. These Pacific islands are closer to North Korea than anywhere on North American continent, so it would require relatively smaller advances in the country’s strike capabilities to put them under real threat. Whether North Korea is already there, close to there, or not close at all remains, however, a matter of conjecture, as all the same technical questions surrounding its ICBM capabilities still apply here.

As for whether the verbal brinksmanship between Trump and Kim Jong Un makes actual war more likely is questionable — fiery rhetoric aside, Trump’s approach doesn’t actually differ that much from his predecessor’s, while North Korea has long argued its development of nuclear weapons is an act of self-defense against American aggression instead of a step toward a preemptive attack.

Photos via Getty Images / Getty Images, Getty Images / Tomohiro Ohsumi