Kim Jong Un may be on a suicide mission, as President Donald Trump told the U.N. General Assembly on Tuesday, but nobody in the White House with a serious understanding of the effect of war with North Korea would approve of a U.S. response that would indulge it, experts say.

Tens of thousands of civilians would likely die in the first hours of a resumption of the Korean War, if only due to the conventional rockets Pyongyang has hidden in the mountains along the Demilitarized Zone and aimed at Seoul. That estimate does not include the 30,000 U.S. forces based on or near the border and the 200,000 American expatriates living in the capital city.

The number also does not account for North Korea's ability to employ nuclear weapons, which could put the overall death toll as high as millions.

And yet, in the most prominent international address of his presidency, Trump on Tuesday escalated the U.S. military threat against Kim's regime.

"If it is forced to defend itself or its allies," Trump said of the U.S., "we will have no choice but to totally destroy North Korea."

The purpose then of Trump's bellicose rhetoric is largely to present military action as what diplomats call a "credible threat," forcing all sides to opt instead for peaceable negotiation. It's a familiar tactic for North Korea, as most experts agree that's what inspired Kim to pursue nuclear weapons in the first place.

"Both sides are fully aware that open hostilities between the U.S. and North Korea would result in catastrophe," says Charles Armstrong, a professor at Columbia University and expert on the region. "A military option is not realistic. Even a limited conflict between the U.S. and North Korea would cause tremendous damage and loss of life."

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Members of the Trump administration have stressed that they are considering military options against North Korea.

National Security Adviser H.R. McMaster said earlier this month that Kim is "going to have to give up his nuclear weapons because the president has said he's not going to tolerate this regime threatening the United States and our citizens with a nuclear weapon." When asked if that included military options, he said Trump has "been very clear about that, that all options are on the table."

U.N. Ambassador Nikki Haley has perhaps been most vocal regarding military actions against Pyongyang.

"If North Korea keeps on with this reckless behavior, if the United States has to defend itself or defend its allies in any way, North Korea will be destroyed. And we all know that, and none of us want that," she said earlier this week.

Defense Secretary Jim Mattis told reporters at the Pentagon on Monday that Haley is correct, but he stressed the importance of focusing on diplomatic solutions.

"There are many military options in concert with our allies that we will take to defend our allies and our own interests," he said.

Mattis repeated assertions from his trip to Mexico on Saturday where he learned that the government there expelled the North Korean delegation there for violating international treaties, as had Peru before it.

"So, yes, it's working," Mattis said.

Perhaps the biggest shortcoming of the Trump administration's policy is that it has not specified what negotiations with North Korea would look like or what terms it would have to comply with before talks could begin. Secretary of State Rex Tillerson has said on multiple occasions and repeated on Sunday, "We'll know it when we see it in terms of their seriousness."

Trump also undercut his own threats by tying North Korean aggression to his criticism of Iran, for which the president has said he wants to tear up an agreement limiting its nuclear program, says Vikram Singh, a former top Pentagon official for Asia issues, now a senior adviser at the Center for American Progress. Pyongyang would have no incentive to enter into an agreement with Washington if it thinks it will be trashed later on.