The Pentagon says it's sending a U.S. aircraft carrier strike group to the waters near the Korean Peninsula. This involves the USS Carl Vinson and the ships escorting it which include destroyers that are capable of shooting down missiles. The group was originally headed from Singapore to Australia, but it changed direction. The reason: provocations by North Korea, according to U.S. defense official.

Tensions on the peninsula are high. South Korea is a U.S. ally. It says the situation is grave and that North Korea might be planning another nuclear test and missile launch in the days ahead.

Japan is a U.S. ally. It says it's getting harder to maintain security in the region and that having U.S. ships in the area is an important deterrent to North Korea.

The communist country has blamed what it calls U.S. aggression for the reason it's trying to develop nuclear weapons. But its program is considered illegal by other countries. As far as the U.S. strike group goes, "The Navy Times", a U.S. military publication, says it's rare for American officials to announce the movements of U.S. aircraft carriers, but that when it is done, it's meant to send a message.

How is North Korea responding?

WILL RIPLEY, cnn INTERNATIONAL CORRESPONDENT: We've been speaking with North Korean officials here in Pyongyang and they tell us that they are receiving the message the United States is sending by deploying that carrier strike group to the waters off the Korean Peninsula and they also believe that the missile attack on that Syrian air base was a direct warning from the Trump administration not only to China but also to North Korea.

But their response may not be what the Trump administration is intending to be. They say, instead of backing down, they want to accelerate their nuclear program and their weapons development. They had said for a long time that they believe the U.S. is hypocritical because it possesses nuclear weapon. It's the only country that has ever used nuclear weapons on civilians.

And they look at what has happened in other countries, like Iraq and Syria, regimes that have been taken down by the U.S. and its allies. They look at the chaos that's happening in Syria and they do not want to see a repeat of that here in North Korea. They say that if the Trump administration would have launched some sort of a preemptive strike here, they would retaliate and that could potentially be very devastating even with the weapons that North Korea possesses right now.

There are tens of millions of people in the greater Seoul area, some 30 miles from the demilitarized zone, well within range of North Korea's conventional weapons, including artillery, that could a lot of damage and kill a lot of people. But it could be even bigger than that, because U.S. and South Korean officials have thought for several weeks now that North Korea is really ready at any time to push the button on its sixth nuclear test.