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First, though, North Korea is accusing the United States of declaring war. There have been a lot of threatening statements between the two countries in recent months, what some observers have been calling a war of words. At the United Nations General Assembly last week, both U.S. President Donald Trump and North Korean Foreign Minister Ri Yong Ho spoke out against each other's country.

Then, over the weekend, President Trump tweeted that if Foreign Minister Ri echoes the thoughts of little rocket man, that's a controversial name that President Trump used for North Korean dictator Kim Jong-un, the North Korean leaders, quote, won't be around much longer.

Foreign Minister Ri called that an American declaration of war on his country and said North Korea would have the right to make, quote, counter measures, including the right to shoot down U.S. bombers at anytime even when they're not in North Korean air space. He was referring to flyovers that U.S. planes recently conducted over international waters east of North Korea.

The U.S. State Department says America has not declared war on North Korea and that it continues to push for a peaceful stop to North Korea's nuclear weapons programs. The U.S. also says it has a right to fly in international airspace and that no country has the right to fire on other nation's planes or ships in international areas.

COL. STEVE WARREN, CNN MILITARY ANALYT: This is a very tense situation and we always hope that cooler heads would prevail.

If we fly more strategic aircraft near the North Koreans and they choose to try and shot one of those aircraft down, this could be a flash point. If the North Koreans feel that they're being overly threatened and choose to fire some sort of rockets, missiles, artillery in to South Korea, and strike American forces. We have just under 30,000, approximately 30,000 U.S. forces station in Korea. This could become a flash point, which will lead to greater trouble.

So, this is a powder keg right now and this is something that we need cooler heads on both sides to be really beginning to prevail here.

SUBTITLE: Why Does North Korea Keep Launching ICBMs?

PAULA HANCOCKS, CNN INTERNATIONAL CORRESPONDENT: Every missile launch by North Korea is considered by most to be a provocation, but it's more worrying than that. Every launch, takes North Korea one step closer to its stated goal of being able to hit mainland United States with a nuclear-tipped missile. Now, the regime has tested intercontinental ballistic missiles this year. The leader Kim Jong-un claims he already has major U.S. cities in his sights.

But how close is he exactly? There are a number of questions that remained to be answered. Does Pyongyang have a warhead that can reenter the earth's atmosphere without burning up? Experts simply don't know.

Does Pyongyang have a nuclear weapon that's small enough to fit on the tip of a missile, i.e., has it miniaturized a nuclear warhead? That Kim Jong-un claims he already has done that, although some experts refute that claim. But U.S. officials say that they have to take Kim at his word. They have to work under the assumption that he has that capability.

Kim hopes that every ICBM test will improve on the last and the closer he get to achieving an effective nuclear arsenal, the harder it will be to convince him to give it up.