President Donald Trump issued an intense warning to North Korea on Tuesday, saying they “best not make any more threats against the United States” lest they “be met with fire and fury unlike the world has ever seen,” according to press pool reports.

Trump’s fiery statement follows a Washington Post report citing a leaked U.S. intelligence memo that acknowledges that North Korea can make nuclear warheads small enough to fit on missiles, and that they may have 60 such devices.

The Trump administration has stressed in recent months that it doesn’t seek regime change in North Korea, but not every voice appears to be on the same page.

Trump’s National Security Advisor, H.R. McMaster, told MSNBC’s Hugh Hewitt that Trump “has been very clear about it: He said he’s not going to tolerate North Korea being able to threaten the United States.”

Experts contacted by Business Insider unanimously state that a war against North Korea would be catastrophic and potentially deadly to millions.

In June, Secretary of Defense Mattis told the House Appropriations Committee that war with North Korea would be “more serious in terms of human suffering than anything we’ve seen since 1953,” and result in “the massive shelling of an ally’s capital, which is one of the most densely packed cities on earth.”

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