"Rocket Man" Kim Jong-un's description of Donald Trump as a "mentally deranged US dotard" marks a significant escalation in the sabre-rattling rhetoric in the Korean nuclear crisis, one which analysts believe heightens the chance of a conflict.
Also significant is a comment by North Korea's foreign minister Ri Yong-ho that his country was considering testing a hydrogen bomb in the Pacific Ocean. This could cross a red line with China, its old ally, which supplies most of North Korea's fuel.
“Whatever Trump might have expected, he will face results beyond his expectation. I will surely and definitely tame the mentally deranged US dotard with fire,” Kim said in a riposte to Trump’s maiden address at the UN, during which he vowed to “totally destroy North Korea” and described Kim as “Rocket Man on a suicide mission”.
Paul Haenle, director of the Carnegie-Tsinghua Center for Global Policy in Beijing, said that to have that kind of statement directly from Kim is quite rare.
"You could argue that if Kim Jong-un is pursuing a nuclear programme to deter an attack, then this kind of language runs the risk of convincing Kim that Trump is planning a pre-emptive strike. If it looks like the US may use pre-emptive measures, it may drive Kim to pre-emptive measures," says Haenle.
Verbal attacks are common from Pyongyang – <a class="search" href='javascript:window.parent.actionEventData({$contentId:"7.1213540", $action:"view", $target:"work"})' polopoly:contentid="7.1213540" polopoly:searchtag="tag_person">George W Bush</a> was described as looking like a 'chicken soaked in the rain'
“You may have a dangerous escalation that results in an outcome we are trying to avoid,” he adds.
The exchange of insults over the past few days has been unprecedented, even in the weird, ill-tempered world of US-North Korean relations, as normally the US leadership rises above it.
Verbal attacks are common from Pyongyang – Barack Obama was called a "dirty fellow" and a "juvenile delinquent" while George W Bush was described as looking like a "chicken soaked in the rain".
The international community is trying to convince North Korea to abandon its nuclear weapons programme after it staged its sixth nuclear test on September 3rd and test-launched a series of missiles, including two over Japan.
The UN Security Council has imposed fresh sanctions, with even China and Russia, who have been lukewarm about the matter, signing up for harsher embargoes.
"China and Russia are united in wanting to prevent the war from happening, even if there is just a 1 per cent chance," said Wang Sheng, a North Korea expert at Jilin University.
Momentous development
For Haenle, another momentous development came when foreign minister Ri said in New York that North Korea may consider its most powerful test of a hydrogen bomb in the Pacific Ocean.
China’s role in the crisis so far has largely been to try to ease tensions and repeatedly call for dialogue, but should North Korea test a bomb in the Pacific, that could lead to China becoming more engaged in the situation.
China provides most of North Korea’s oil, but so far it has refused to cut off supply because it would only alienate Pyongyang and create an enemy on its border.
“According to Chinese experts, the sixth nuclear test did not cross a red line for the Chinese. However, any nuclear test where fallout comes into Chinese territory, or if North Korea tests a ballistic missile with nukes that lands in the Pacific Ocean, that threatens a Chinese red line and the Chinese could respond by cutting of North Korea’s oil,” says Haenle.