Michael Schmitt, from the United States Naval War College, says he believes the world is at a dangerous moment in time, as tensions escalate dramatically between North Korea and the US over Pyongyang's missile and nuclear weapons program.
"We have a leader in North Korea who's not entirely rational," Professor Schmitt told SBS World News.
"He's not a rational actor, so one has to wonder at what point he will be set off and conduct some operation against South Korea, or against United States forces either in Guam or in South Korea."
Professor Schmitt was speaking just hours after US President Donald Trump warned North Korea would be met with "fire and fury, like the world has never seen" if it made any more threats against his country.
The day before North Korean State Television warned the villainous and illegal actions by the US - referring to its drafting of tough new UN sanctions on the weekend - would be reciprocated thousands of times over.
Professor Schmitt warned against the language being used by the United States.
"I think we need to tone down the rhetoric a little bit, because if you're dealing with the leader of an opposing country, who's not entirely rational, it doesn't help to engage in bombastic comments," he said.
"The first thing we can do is tone down the rhetoric and then we need to place the leadership of North Korea on notice of where our red lines are.
"What we would consider to be a red line, what our capabilities are and we need to convince that leader (of North Korea) that we're willing to employ those capabilities in the event that red line is crossed."
Professor Schmitt said he was confident President Trump would be getting sound advice from people within his administration.
"I think we have a fair number of rational players in the United States and Washington," he said.
"I would cite, for example, the Secretary of Defence (James Mattis) who's a very experienced military leader, he's very comfortable dealing with a crisis. So, at least with respect to the Secretary of Defence, I'm comfortable that the President will be getting good advice. And, of course, scattered throughout the State Department and the Department of Defence, we have very sophisticated individuals."
"I do think they (Donald Trump's comments) are more than just bluster. I believe the president would be willing to order US military forces into action. I believe, though, that the superb attorneys at the State Department and at the Department of Defence would make clear to the president the precise preconditions needed to order forces into action."
The strong words from Mr Trump were followed by another threat from Pyongyang, with the official news agency saying it was considering a plan to fire medium-to-long-range rockets at Guam, where US strategic bombers are based.
Professor Schmitt said such an action would inevitably provoke a response.
"I'm absolutely convinced that in the event of a strike against US forces on Guam, or anywhere else, or in the event of a strike against any of our allies in the region, particularly Japan or South Korea, that we would respond," Professor Schmitt said.
"Whether we would respond in a manner that takes the current leadership out of power in North Korea, I don't know. But there's not doubt in my mind that we would respond, pursuant to the right of self defence under international law.
"They (the response) could be surgical strikes taking out the capabilities that the North Koreans have to conduct further attack, it might be an operation that's a bit more robust to impose cost on the North Korean leader. I don't know that we would go to war in a classic total war sense with North Korea. I think that is unlikely."
Additional reporting Rhiannon Elston
