According to the Washington Post, Pentagon officials have warned that the only way to locate and secure North Korea's nuclear weapons sites would be via a ground invasion.
'A classified briefing would be the best place to discuss in detail the capability of the USA and its allies to discuss capabilities to counter North Korea's ability to respond with a nuclear weapon and eliminate North Korea's nuclear weapons located in deeply buried, underground facilities, ' he said.
"There's a danger if there is a lot of muscle-flexing", said Mike Chinoy, senior fellow at the University of Southern California's U.S.
That blunt assessment from the Pentagon is in response to a letter from two Democratic congressmen asking about casualty assessments in a conflict with North Korea.
The president's first stops are Japan and South Korea - frontline USA allies in the effort to force Pyongyang to abandon its nuclear programme, and the two countries with most to fear should a full-scale conflict break out.More news: Florida State University student dead after apparent party
In June, the Treasury Department declared the Bank of Dandong a "primary money laundering concern" for serving as a gateway for North Korea to access the U.S. and worldwide financial systems despite USA and United Nations sanctions.
But as the president prepares to meet South Korean President Moon Jae-in, a report by a South Korean spy agency Thursday said there was "active movement" surrounding a missile research facility in Pyongyang. Former North Korean diplomat Thae Yong Ho warned USA lawmakers that they would "press the button without further instructions" and suggested that military action against Kim would nearly certainly result in a catastrophic number of civilian casualties.
In a June article in Bulletin of the Atomic Scientists, the military historian Reid Kirby said the types of artillery along the demilitarized zone, and vulnerability of children and the elderly, meant that a North Korean attack using the nerve agent Sarin could kill as many as 2.5 million people in Seoul and injure millions more.
There are about 18,000 civil defense shelters across South Korea.
North Korea's last nuclear and missile tests both occurred in September. On Sept. 3, Pyongyang conducted its sixth nuclear test.More news: Former Trump adviser Roger Stone suspended from Twitter…again
President Donald Trump shakes hands with Japan's Prime Minister Shinzo Abe (R) during a news conference at Akasaka Palace in Tokyo on November 6, 2017.
Trump has previously said that Secretary of State Rex Tillerson was "wasting his time" trying to negotiate with Kim, belittling previous negotiation efforts and adding that "only one thing will work".
It comes after a series of missile and nuclear tests in the past few months, a sharp escalation from recent years.
And while the foreign minister acknowledged that some of Trump's rhetoric had raised anxieties in South Korea, she stressed that her government was focused on the president's "overall tone".
'There is only one way that this war ends. It also wants nothing short of full normalization of relations with the USA and to be treated with respect and as an equal in the global arena.More news: Ten year old boy led police on a high speed vehicle chase