North Korea has suggested that it could test a hydrogen bomb in the Pacific, the latest in an escalating tit-for-tat between leader Kim Jong Un and President Trump.
If Pyongyang makes good on the threat, it would mean marrying the two most powerful weapons known to man: a fusion-type nuclear weapon and a ballistic missile.
"This could probably mean the strongest hydrogen bomb test over the Pacific Ocean," North Korean Foreign Minister Ri Yong Ho told reporters in New York on Thursday in response to a question about what action the regime might take against the U.S.
"Regarding which measures to take, I don't really know since it is what Kim Jong Un does," Ri said.
He spoke just days after Trump, in a speech before the United Nations General Assembly, derisively called Kim "Rocket Man" and said it might be necessary to "completely destroy" North Korea.
The president's bellicose rhetoric was in turn answered by Kim in a rare personal statement broadcast on state television. Kim described Trump as "a madman" and "a frightened dog" and "a mentally deranged U.S. dotard."
"I will make the man holding the prerogative of the supreme command in the U.S. pay dearly for his speech calling for totally destroying [North Korea]," Kim said.
On Friday, Trump apparently responded in a tweet, saying Kim "will be tested like never before!"
Secretary of State Rex Tillerson on Friday appeared to try to soften the rhetoric. Appearing on ABC News, he emphasized the administration's diplomatic efforts and economic sanctions aimed at taming Pyongyang's nuclear ambitions.
"The president obviously takes very seriously the security of the American people. But we are not in this alone. We have strong allies and strong alliances internationally. And we are engaging with North Korea's most important supporters, economic supporters — their friends, China and Russia to have them engage with Kim Jong Un on this issue," Tillerson said.
Following Trump's U.N. speech, China's English-language edition of the state-run People's Daily in an editorial called the president's remarks "political chest-thumping [that] is unhelpful."
"It will only push [North Korea] to pursue even riskier policies, because the survival of the regime is at stake."
Pressed on what the administration's response would be if North Korea went ahead with the test of a hydrogen bomb, the secretary of state said "all of our military options" are "on the table."
"Once we can assess the nature of this threat, the president will make a decision regarding the appropriate actions," Tillerson said, adding that Trump would receive advice from the National Security Council and others but that, "ultimately, it will be his decision."
In an executive order issued Thursday, the Treasury Department has been granted expanded latitude to target anyone trading with North Korea, barring them from using the U.S. banking system.
The latest threats of a bomb-and-missile test coming out of Pyongyang, as NPR's Geoff Brumfiel reported earlier this month, raises the specter not seen since the height of the Cold War. In a one-and-only such test in 1962, the U.S. launched a nuclear-tipped ballistic missile from a submerged submarine.
As Geoff writes:
"There are good reasons why nuclear weapons and nuclear missiles are usually tested separately. Nuclear weapons are the most powerful devices ever developed by human beings. Missiles are giant tubes filled with explosive fuel. Bringing the two together is risky enough. Firing the missile increases the risk considerably."