North Korea has threatened to launch a strike on the USA territory with "medium-to-long-range strategic ballistic missiles", according to KCNA.
There were no signs of panic or an exodus from the island of 163,000 people on Thursday, with its wide roads clogged with commuters and commercial vehicles and shops and restaurants doing brisk trade from South Korean and Japanese tourists drawn to the island's green hills and bright turquoise waters.
Nationalists claim that it is because of the U.S. military that the island attracts potential threats.
"I'm not really too anxious about it. I feel like moving (out of Guam) now". Some people are just - we just want our place. Later, Defense Secretary James Mattis warned North Korea in a statement it would lose any conflict it initiates.
U.S. President Donald Trump said North Korean leader Kim Jong Un was not going to get away with his "horrific" comments and disrespecting America.
The drill coincides with the four-day "Ulji Freedom Guardian" military manoeuvres on August 21-24, which are held yearly and include joint exercises by the US and South Korean armed forces, as well as drills for emergencies.
Even though missiles from the North would nearly certainly carry dummy warheads, analysts said, a failure to intercept them would deal Mr. Trump a mortifying setback and could even weaken the rationale for installing an American missile defense system in South Korea.
The lives of the people in South Korea should not be threatened by the provocative acts of the USA and North Korea, said the letter.
"It's business as usual in paradise", said Josh Tyquengco, marketing director at Guam Visitors Bureau, the official agency for the island. He seems to have the technical capacity to make good on this threat: his regime has made observable progress in its missile program, notably firing two intercontinental ballistic missiles last month theoretically capable of reaching the American mainland.
With liberals back in charge in South Korea, Seoul is making peace offerings to its archrivals, but the North isn't biting.
Officials in Guam are giving citizens advice on how to survive such an attack.
Other residents are anxious about the political atmosphere and the government's ability to find a peaceful solution.
"There is no panic in Guam", Calvo told CNN.
"For me because I'm a father, so it's really concerning, you know, I wish it didn't have to come to that", he said. "We know that any moment, they could send those (weapons). but I think a lot of us in the end are not too anxious".
His brother Mitch Thompson, who also lives on Guam, added he believes "a lot of people have no confidence that the White House will do the right thing under the circumstances".
Abe says: "I will do everything, to the best of my ability, to protect the safety and property of the Japanese people".
Guam is about 2,100 miles (3,380 kilometers) southeast of Pyongyang and 3,800 miles (6,115 kilometers) west of Honolulu in the Pacific Ocean.
For Pyongyang, Guam is seen as a prime target because it's the closest United States military presence on American soil to North Korea, and because military assets from here are sometimes deployed near the Korean Peninsula.
The North Korean government responded by stating it is "carefully examining" a plan to hit the US territory of Guam with missiles. "To make matters worse, President Trump has declared that "North Korea would face fire and fury, one never witnessed by the world", states the letter.
Clarissa Baumgartner, a 25-year old Guam resident, said Pyongyang's second threat in as many days to train its ballistic missiles on Guam wasn't something she was taking too seriously.
"We're told to keep calm and that we're well-protected, but the reality is we could be here today and gone tomorrow", she said.
With its latest threat, North Korea is suggesting it could launch four missiles which could potentially overwhelm the THAAD missile defense system and strike near Guam.
South Korea's conservatives want still more sanctions and pressure; they call his pleas for talks a "one-sided love affair".