THE launch of a ballistic missile on July 28th, with the range to hit cities on America’s west coast, provided further chilling evidence of the speed at which North Korea is developing a capability that Donald Trump has declared it would never have. It followed a test of a similar Hwasong-14 two-stage missile on July 4th. Both launches were on a lofted trajectory—the missile travelling more or less straight up rather than around the curve of the Earth. Based on the test’s course and flight time, analysts believe the first missile would have had a normal-trajectory range of about 7,500km, while the second, which flew for 47 minutes and reached an altitude of 3,700km, would have had a range of up to 10,000km while carrying a warhead weighing up to 650kg.

It is too soon, however, to assert that North Korea is on the brink of being able to threaten, say, Los Angeles, with a reliable intercontinental ballistic missile (ICBM). To do so, it would need to make a warhead compact and light enough to fit into a missile’s nose cone.

Experts, such as Jeffrey Lewis of the James Martin Centre for Non-Proliferation Studies in California, believe that North Korea can already fit a fission nuclear warhead with a yield of about 20 kilotonnes, the same as the atomic bomb dropped on Nagasaki, to its short- and medium-range missiles. But so far, there is nothing to suggest that it has yet tested a fusion or thermonuclear weapon despite claims by its leader, Kim Jong Un, that it has. It is clearly working on the technology, though. It may be able to demonstrate this, or at least add a thermonuclear element to boost yield, when it conducts a sixth nuclear test, perhaps before the end of the year. A thermonuclear warhead small enough to be carried by the Hwasong-14 could easily have a yield of 300 kilotonnes, enough to devastate an area of over 70 square kilometres.

There is also scepticism that North Korea has yet produced a re-entry vehicle that would protect the warhead on its path through the Earth’s atmosphere at velocities travelled by ICBMs. In an analysis of the latest launch, Michael Elleman of the International Institute for Strategic Studies has examined video from a weather camera in Hokkaido, Japan, which captured the glowing re-entry vehicle on film as it sped earthwards. As it hits the Earth’s atmosphere, it starts to shed “small radiant objects” and “incandescent vapour”. It then dims and disappears. Based on its current progress, North Korea will probably overcome such problems sooner rather than later. The latest assessment by America’s Defence Intelligence Agency, reported by the Washington Post three days before the most recent missile test, is that North Korea could have a workable ICBM some time in 2018—at least two years before the previous consensus had estimated it would do so. The reactions to the missile test were mostly predictable. Two B1 strategic bombers were dispatched from an American base in Guam to fly over South Korea. A THAAD anti-missile battery in Alaska, like the one recently deployed in South Korea, successfully carried out a test interception. In two tweets Mr Trump wrote: “I am very disappointed in China. Our foolish past leaders have allowed them to make hundreds of billions of dollars a year in trade, yet…they do NOTHING for us with North Korea, just talk. We will no longer allow this to continue. China could easily solve this problem!” A few days later Rex Tillerson, America’s secretary of state, struck a more emollient note towards North Korea, saying: “We do not seek a regime change…we hope that at some point they will begin to understand that and we would like to sit and have a dialogue with them.”

Paradoxically, in South Korea, conservative opposition parties have called on the country’s recently elected liberal president, Moon Jae-in, to abandon his twin-track policy of imposing sanctions on North Korea while still offering dialogue. Mr Moon wants to see a greater level of military readiness for anything that might happen. But, like Mr Tillerson, he is still insisting that he would not close the door on talks with Mr Kim, should he respond. Among the options under consideration is a relaxation of an agreement between America and South Korea that limits the range and payload of the South’s conventional missiles.

If the reaction to the test on July 28th consisted largely of gestures and vague threats, that is because the options are either improbable (constructive talks with Mr Kim), feeble (tougher sanctions) or terrifying (pre-emptive military action).

For all that, fears are growing that Mr Kim and Mr Trump are now on a collision course which could result in a war that neither wants, but which both may find difficult to avoid. Rodger Baker of Stratfor, a geopolitical consulting firm, says that Mr Kim wants to prove he has a credible ICBM capability, while America has to show that it has the military will to prevent it. He believes that North Korea would have to respond in some way to an American strike, even of the most limited kind.

Anthony Cordesman of the Centre for Strategic and International Studies in Washington, DC, warns that America’s ability to deal with all North Korea’s nuclear facilities “is very uncertain”. He adds that anticipating what the North might do with its conventional weapons is like “trying to describe a very complex game of multidimensional chess in terms tic-tac-toe”. The problem, he says, is that there are many ways and reasons for each side to escalate the fighting once it begins. Stopping it would be much more difficult.

People with military experience of Korea “paint a picture that should scare the hell out of anyone in the US who was contemplating an attack,” says Jonathan Pollack of the Brookings Institution. “Are we over-estimating North Korea?” he asks. “I don’t want to find out.”