Known as the 'Tip of the Spear', Guam, just a speck in the Pacific Ocean, is vital to the US military's presence in the region and is home to thousands of American service members and key bases.

It’s little wonder that the airbase, which allows the US to project its vast military presence across the Asia-Pacific, “gets on the nerves” of Kim Jong-un, whose regime today threatened to attack the atoll.

North Korea's statement came shortly after Donald Trump threatened to visit upon the rogue state "fire and fury like the world has never seen" early this morning.

Security and defence officials on Guam say there is no imminent threat to people there or in the Northern Mariana Islands after North Korea said it was examining its operational plans for attack, reports AP.

Guam's Department of Homeland Security and Office of Civil Defense says it is monitoring North Korea with U.S. military and government officials.

Guam's Homeland Security Adviser George Charfauros says officials there are confident "the U.S. Department of Defense is monitoring this situation very closely and is maintaining a condition of readiness."

Charfauros in his statement Wednesday morning urged calm and said defences are in place on Guam and its neighboring Pacific islands for threats such as North Korea.

Trump’s blast followed reports that North Korea, which has lately made appreciable progress with its ICBM program, may have finally succeeded in miniaturising a nuclear warhead, and could have a stockpile of dozens of nuclear devices.

Tension in the region, which has been ratcheting up to near-unbearable levels in recent months, was further inflamed on Monday when the US flew two B1B bombers from the Andersen airbase on Guam over the Korean peninsula.

Guam is home to thousands of US service personnel and key military bases. (Supplied).

Located 5300kms west of Hawaii, Guam enables the US to project its vast military assets into the Asia-Pacific region.

The island measures just 58kms in length and 20kms across but is big enough for the US Army anti-missile system, the Andersen Air Force Base and a major naval port at Apra Harbor.

Other US military assets at Guam include Los Angeles class submarines and the specialist Naval Special Warfare Unit One, part of the renowned SEALs.

In 2014, the Pentagon announced a long term plan to relocate 8000 marines from bases in Japan to Guam as well as Northern Australia and Hawaii.

In 2013, in response to threats from North Korea, the US Army began deploying the terminal high-altitude area defence battery, or THAAD to Guam.

THAAD is a land-based element that can shoot down a ballistic missile inside and just outside the atmosphere and would be the frontline weapon in meeting any North Korean strike.

US Air Force B1B bombers, based at Guam, have flown over the Korean peninsula. (Supplied).

In another statement citing a different military spokesman, North Korea also accused the US of devising a "preventive war" and said any plans to execute this would be met with an "all-out war wiping out all the strongholds of enemies, including the US mainland".

The UN Security Council unanimously imposed new sanctions on North Korea on Saturday over its continued missile tests.