The United States will defend its allies and itself if North Korea goes ahead and carries out its threat of launching war against its southern neighbour, John Kerry, the US secretary of state, has said.
Kerry, on a three-day visit to South Korea, Japan and China to find a solution to tensions on the Korean peninsula, said on Friday that Pyongyang would not be accepted as a nuclear power.
If North Korea decides to fire a missile, it will be "one more unnecessary, unwanted" provocation and it would "indicate who is being provocative with an exclamation point yet again", said Kerry.
"The rhetoric that we are hearing from North Korea is simply unacceptable by any standards," he told a news conference in Seoul alongside Yun Byung-se, the South Korean foreign minister.
"The United States, South Korea and the entire international community... are all united in the fact that North Korea will not be accepted as a nuclear power," Kerry added.
He said more rounds of talks with North Korea to resolve the tensions would be welcome but warned that "no one is going to talk for sake of talking".
Earlier, Yun said he had a "very progressive" meeting with Kerry and that five positions regarding North Korea had been agreed but he did not give details of those positions.
Follow coverage of escalating threats in Northeast Asia
"The [North Korean] threat was taken as a threat to the general public. We expect the North to comply with the South efforts to engage in dialogue," he said.
"The plan going ahead is to analyse what has happened today and to arrive at a definitive position."
Yun also said he and his guest had the opportunity to discuss the situation in Syria, climate change and other matters.
Meanwhile, Japan on Friday vowed it would respond to "any scenario" after a threat by North Korea that Tokyo would be "consumed in nuclear flames".
"All we can say is we will take every possible measure to respond to any scenario," a defence ministry official told the AFP news agency.
Republican US Senator John McCain said an attack carried out by North Korea would be "suicidal".
"I don’t believe North Korea would launch an attack, because it is suicidal, but to be certain of the behaviour of a regime like this to be bound by rational thought and action I think is a serious mistake," he told Al Jazeera.
US Senator John McCain talks to Al Jazeera
McCain said that with artillery stored in caves in the Demilitarised Zone, North Korea "has the ability to fire quite a bit before they are taken out".
"There is no doubt the N Koreans would lose but what kind of damage could they do in that period of time? It could be horrendous."
Kerry's visit came as both South Korea and Washington continued joint military exercises that North Korea says are intended to pave the way for an attack against it, Al Jazeera's Marga Ortigas reported from Seoul.
"It’s precisely because these joint military exercises continued that North Korea amped up its angry rhetoric. They [North Koreans] have been saying that this is just a ruse to try to plan an invasion of North Korea," she said.
North Korea carried out its third nuclear test in February, prompting fresh UN Security Council sanctions resolution against the impoverished and reclusive state.
Barack Obama, the US president, has also weighed in, calling on North Korea to end its "belligerent approach".
Obama made his remarks as the Pentagon backed away from an intelligence report which suggested North Korea might have developed nuclear weapons which could be fit onto a ballistic missile.
Pentagon spokesman George Little said "it would be inaccurate to suggest that the North Korean regime has fully tested, developed, or demonstrated the kinds of nuclear capabilities referenced in" the intelligence report.
The statement came after a legislator read out the findings of a Defence Intelligence Agency (DIA) report at a congressional hearing earlier on Thursday that appeared to signal a shift in Washington's view of North Korea's nuclear
The DIA assessment said US analysts had "moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles" but that the reliability of the weapons was "low".
The intelligence report marked the first time the US government had suggested North Korea may have succeeded in a years-long quest to miniaturise a nuclear device so that it could be placed on a missile.