The general in command of US nuclear forces said Saturday that he would resist any "illegal" presidential order for a strike and work to find an alternative.
President Donald Trump's history of unpredictable and volatile behavior has raised concerns that he could unilaterally order an unnecessary nuclear attack -- an issue recently debated by members of the US Senate.
"We think about these things a lot. When you have this responsibility, how do you not think about it?" General John Hyten told the Halifax Security Forum in response to a question about the conversation he would have with the president on a potential strike.
"I provide advice to the president, he'll tell me what to do."
Hyten heads US Strategic Command, which is responsible for American cyber capabilities and missile defense, in addition to nuclear weapons.
"If it's illegal... I'm gonna say, 'Mr President, that's illegal.' And guess what he's gonna do? He's gonna say, 'What would be legal?' And we'll come up with options, of a mix of capabilities, to respond to whatever the situation is," Hyten said.
Trump issued an apocalyptic threat to unleash "fire and fury" on North Korea and began calling Kim Jong-Un "Rocket Man" after a series of provocative missile tests, while the hermit state's leader branded Trump a "dotard."
The escalating war of words has alarmed some US lawmakers, and senators debated the limits of a president's unilateral power to launch a nuclear attack earlier this week.
In the event of an ongoing or imminent nuclear attack, senators and expert witnesses agreed that the president had full authority to defend the nation, but experts said there was no strict definition of "imminent."
As to what constitutes an illegal order, Hyten referred to the four key principles from the Law of Armed Conflict in his remarks.
"The Law of Armed Conflict has certain principles -- necessity, distinction, proportionality, unnecessary suffering -- all those things are defined," said Hyten.
"If you execute an unlawful order, you will go to jail, you could go to jail for the rest of your life. It applies to nuclear weapons, it applies to small arms, it applies to small unit tactics, it applies to everything."
© 2017 AFP