The escalation in the war of words comes after President Donald Trump tweeted Kim Jong Un "won't be around much longer."
A long war between the United States and North Korea is "now a real possibility," a respected British think tank concluded this week.
"Casualties in such a conflict would likely reach the hundreds of thousands, even if no nuclear weapons were used," according to a report by the Royal United Services Institute (RUSI).
"There could be far-reaching consequences for the global economy, involving sustained disruption of vital supply chains and markets," the report said.
The report came as US President Donald Trump backed away from a threat to skip the ASEAN summit claiming the visit will strengthen the international resolve against North Korea, reports News.com.au.
In a statement on Friday, the White House said that Mr Trump will visit the summit with South East Asian leaders in the Philippines as part of a bumper November 3-14 tour that will also include stops in China, Japan, South Korea, Vietnam and the US state of Hawaii.
The White House said the president's visit would "strengthen the international resolve to confront the North Korean threat and ensure the complete, verifiable, and irreversible denuclearisation of the Korean Peninsula."
Mr Trump has offered fiery rhetoric and a tough stance against the North's nuclear weapons program, declaring in a speech to the United Nations General Assembly last week that the US would "totally destroy" North Korea if provoked.
This undated file photo distributed by the North Korean government shows what was said to be the test launch of an intermediate range Hwasong-12 in North Korea. Photo / AP
North Korea responded with pledges to take the "highest-level" action against the United States and warned that it might conduct the "most powerful" atmospheric hydrogen bomb test in the Pacific Ocean.
According to the RUSI report Pyongyang could strike first if it believes the US was planning a surprise attack, or Washington could draw first blood if the rogue regime test-fires missiles near Guam or California.
"This report is not saying that war is likely. But the probability of war is an uncomfortably real prospect," said RUSI deputy chief Malcolm Chalmers, who authored the report. "If this war is launched, it will not be surgical or short."
If incited, the US would likely launch a major attack - with aerial and cyber attacks - with a goal of disabling or destroying North Korea's military infrastructure, the report said.
Meanwhile, Mr Trump's trip to the ASEAN sets up the likelihood that he will meet controversial firebrand Filipino President Rodrigo Duterte.
During a visit to ASEAN's Jakarta headquarters in April, Vice President Mike Pence had promised allies - anxious about waning US engagement in the region - that Mr Trump would attend the bloc's summit in Manila this November.
Mr Trump will likely meet controversial firebrand Filipino President Rodrigo Duterte at ASEAN. Photo / AP
But Mr Trump's souring bromance with host Mr Duterte, and a range of other issues had briefly thrown those plans in the air.
Mr Trump said earlier this month that Mr Duterte had extended an invitation, but that he had not yet decided whether to accept.
"He invited us so we're going to see," Mr Trump said, while announcing he would go to Japan, South Korea, China and, maybe, Vietnam for a regional economic summit.
Philippine officials were surprised by the about face and the issue was raised during foreign minister Alan Peter Cayetano's visit to Washington on Wednesday.
Early in his tenure, Mr Trump courted controversy by praising Mr Duterte for doing an "unbelievable job on the drug problem."
