Altogether, 7,000 USA military personnel are stationed on Guam.
Hours after President Donald Trump threatened North Korea with fire and fury like the world has never known, Pyongyang announced it is "examining the operational plan" to attack Guam, a tiny USA territory located in the Pacific.
The North Korean also unveiled another plan to "give stronger confidence in certain victory and courage" to their people.
Guam is home to about 163,000 people and a USA military base.
Preemptive strikes, the statement added, were "no longer the monopoly of the U.S".
"The United States will consider it an apparent attack if it lands within its territorial waters and, given the risks involved, will most likely try to shoot them down before they land anywhere close to Guam and its territorial sea", Lee told Reuters. US commanders refer to Guam as a "permanent aircraft carrier".
USA forces on the island were not immediately available for comment.
"We keep closely watching the speech and behavior of the USA", it said.
After the end of the Cold War, the military started to downsize operations.
Today, there is a continuous bomber presence.
The United Nations Security Council unanimously imposed new sanctions on North Korea on Saturday that could slash its $3 billion annual export revenue by a third.
The U.S. uses the island for war games and joint exercises.
There are two major bases on Guam: Andersen Air Force Base in the north and Naval Base Guam in the south.
Most experts agree that North Korea could have a nuclear warhead small enough to fit on a missile.
"Is the United States indeed the only one with the option of what it calls a preventive war?" Ballistic missiles such as those North Korea has fired go high into space, where satellites are operating. "Guam and Puerto Rico both, a lot of people don't even think about us". Lockheed Martin, Raytheon, General Dynamics and Northrop Grumman were all up, lifting the Dow Jones U.S. defense index 1.17 percent.
There is a sense of patriotism among those who cite the island's history of Guam residents serving in the USA military. Chamorros are the indigenous people of Guam.
On Friday, President Donald Trump urged North Korean leader Kim Jong-Un not to take any action against the U.S., its territories including Guam or its allies, warning he would regret such a move - and "regret it fast". When news broke of North Korea's threat broke, he says he was distraught. "Now that said, you do need to track their threats". The Hwasong-12 it has threatened to lob toward Guam has failed three out of four tests.
Guam officials have reassured residents that defenses are in place and they don't believe an attack is imminent.
GENEREUX: I've had a couple customers say that, like, if it happens and we find out we got 10 minutes left, we're going to come down here and have some drinks with you guys. 'Everyone's afraid, because we're dealing with powers that's beyond us'.
"Unfortunately, there seems to be no serious dialogue between Washington and Pyongyang, only threats", he said.
"I am relying on the THAAD system to stop that", said former University of Guam President Wilifred Leon Guerrero.
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