Donald Trump has previously promised “fire and fury” if the hermit state continues its provocations.
But the US has not acted yet to shoot down one of Kim Jong-un’s missiles, partly because they have not been a threat but also because its own defences are unreliable.
America has a range of Patriot and sea-based Aegis systems that can use interceptor rockets to hit enemy missiles as they descend through the atmosphere.
It also operates a THAAD (Terminal High Altitude Area Defence) system to defend its Pacific island of Guam and part of South Korea.
The Guam weapons can intercept multiple targets launched from Pyongyang but only protect small areas close to where they are based because of a relatively short 124-mile range.
Aegis weapons would be a surer bet, with equipped destroyers patrolling the region an carrying SM-3 mid-course interceptors.
Those weapons are capable of taking down a missile at longer range before it re-enters the earth’s atmosphere.
In all, the US has 33 Aegis warships, with more to come, capable of firing interceptors that can hit a mid or intermediate-range missile like the Hwasong-14.
But Bruce Bennett, an analyst from the Rand Corporation, cast doubt on their reliability.
He told CNN last month: “This is an experimental system.
“We could potentially miss or hit, we don’t know for sure.
“And even people who make cell phones, who have substantially more testing than THAAD does, sometimes have cell phones burn up.”
A failed attempt to shoot one down could even hand Kim Jong-un a propaganda victory, experts say.
In fact, despite Defence Secretary Jim Mattis’ threats to shoot down missiles aimed at Guam, the systems are notoriously unreliable.
Since 2002, 37 tests have been carried out to intercept a mid-range missile with an SM-3 and 29 were successful
But the SM-3 IIA, the USA’s most advanced intermediate range interceptor, has been tested just twice, with only one successfully hitting its target.
In the meantime, higher tech systems currently appear to be out of the USA’s reach, not least because of their eye-watering cost.
So-called boost-phase systems, for instance, are capable of stopping ballistic missiles early in their flight as they climb into the upper atmosphere.
But, despite occasional talk of introducing a worldwide network of the interceptors, they seem out of reach financially.
The US has even built a prototype for a huge airborne laser housed in a Boeing 747.
The weapon, which would need to be located near enemy territory, can burn straight through a missile early in its flight. But again the huge cost appears mohave sunk the project.