Transcript for Trump's threat a 'load of nonsense': North Korea military

But first to new developments on North Korea. We want you to take a live look at Guam where it is nighttime right now. That is the U.S. Tartaglione in the pacific home to thousands of Americans that North Korea threatened to launch missiles toward last night, of course, their response to the president's's fire and fury warning and also calling it a load of nonsense as defense secretary James Mattis warns against any actions that lead to the destruction of North Korea's people. Martha Raddatz tracking all the latest and starts us off from Washington. Good morning, Martha. Reporter: Good morning, George. This is truly a war of words between Donald Trump and north Korea's leader but it could have very real consequences. A yours territory is facing a very specific threat from north Korea in response to Donald Trump's strong words. A defiant rebuke by North Korea. In a statement calling president trump's recent comments a load of nonsense, saying the president is a guy bereft of reason and only absolute force can work on him. And this morning, a renewed specific threat to Guam. North Korea announcing it will launch four missiles at the waters near the island by mid-august. Overnight the governor of Guam responding encouraging calm. There is concern and worry but there is no panic. Reporter: South Korea warning of strong and resolute retaliation for any attack against them or the U.S. The new north Korean threat coming in response to that fiery warning by president trump. North Korea best not make any more threats to the united States. Th will be met with fire and fury like the world has never seen. Reporter: In a statement defense secretary James Mattis backing up the commander in chief but stressing defense saying that the U.S. Has unquestionable commitment to defe ourselves from an attack and that North Korea should cease any consideration of actions that would lead to the end of its regime and the destruction of its people. And in Pyongyang on Wednesday, a rallying call. Thousands of north Korean citizens packing the square in that nation's capital in a display of unity. The increasingly threatening rhetoric coming as U.S. Intelligence analysts now believe scientists in north Korea can produce miniature nuclear warheads that can fit inside those icbm missiles. Kim Jong-un launched two of them last month. But for now all eyes focused on Guam because the threat was so specific, saying four missiles giving an approximate date and saying the waters, not the island itself. This may increase the likelihood they may actually do this, George. Okay, Martha, let's talk about it more with Steve ganyard. Steve, as Martha said it's a specific provocation. Four or five missiles towards Guam in the next couple of weeks and a warning against it from both South Korea and Japan. Yeah, George, the specificity is interesting. Not only does it guess anything state the kind of missile, it says four and the parts of Japan it will overfly and what the intent is so I think what we're looking at is part of the continuing test program because this missile that they're talking about has been very unreliable and never launched it in salvo, in multiples so could be a convenient choice to test it further. It's supposed to go over international waters and the other areas but could get close to U.S. Territory if it gets within the U.S. Territorial waters. What do we do? George, there's a Thad missile system, a new defensive missile system that we talked about in South Korea before. It's intended to defend areas. A good missile to have there. The problem is it's still a developmental missile and although it has 100% success rate it's never been tested against four and the north Koreans know that. But as you know, the real concern here is Guam is American territory and the north Koreans miscalculate that's an act of war. So take us inside the decision-making process, inside the government as North Korea prepares for this. They'll be watching every second of every day but how will they make the decision whether or not the test requires a response? The radars that will pick up the launch from North Korea will hand off that data as the missile travels towards Guam and this Thad missile system is very sophisticated and it'll operate almost on automatic mode and so it sees that missile coming in, the press, I'm sure, will authorize if they do see one coming in they're authorized to knock it down so a lot will be automated and data that will be passed off through a series of radars out in the western pacific. Tensions are getting high, Steve ganyard, thanks very much.

This transcript has been automatically generated and may not be 100% accurate.