Key moments in missile tests

August 8 – Following reports that North Korea had developed a miniaturised nuclear warhead that can fit inside its missiles, Donald Trump says any escalation in hostilities would “be met with fire, fury and frankly power, the likes of which the world has never seen before”.

August 9 – North Korea says it is examining its operational plans for attacking Guam, with the state-run news agency reporting the army said the move was in response to a recent US intercontinental ballistic missile test and it was studying a plan to create an “enveloping fire” in areas around Guam with medium to longrange missiles. US Secretary of State Rex Tillerson says he does not believe there is “any imminent threat” from North Korea, and “Americans should sleep well at night”. He added: “What the president is doing is sending a strong message to North Korea in language that Kim Jong Un can understand, because he doesn’t seem to understand diplomatic language.”

August 13 – Foreign Secretary Boris Johnson, having spoken to US President Donald Trump, posts on Twitter that “the North Korean regime is the cause of this problem and they must fix it”. He urges both sides to avoid words or actions that could worsen the situation.

August 15 – North Korea’s military presents leader Kim Jong Un with plans to launch missiles into waters near Guam and “wring the windpipes of the Yankees”.

August 28 – Mr Johnson speaks of “reckless provocation” as Pyongyang launches a missile between the Korean peninsula and Japan. The device flew over the Japanese island of Hokkaido, before ditching into the Pacific Ocean.

August 30 – Mr Trump tweets “talking is not the answer”, saying his country and North Korea had been engaged in dialogue for 25 years and paying them what he called “extortion money”.

September 3 – North Korea carries out its latest nuclear test at the Punggye-ri site where it has conducted many of its previous tests. North Korea said it was a hydrogen bomb meant for an intercontinental ballistic missile, while South Korea said it recorded a 5.6-magnitude earthquake – later revised by the US Geological Survey to 6.3 – which was triggered artificially, suggesting a device had been detonated.