The threat came hours after US President Donald Trump threatened Pyongyang with "fire and fury" over its missile program and days after the UN Security Council levied new sanctions on North Korea over its growing nuclear arsenal.
Pyongyang said it's "now carefully examining the operational plan for making an enveloping fire at the areas around Guam with medium-to-long-range strategic ballistic rocket Hwasong-12," according to the official Korean Central News Agency (KCNA).
The plan will be finalised "and will be put into practice in a multi-concurrent and consecutive way any moment once Kim Jong-un, supreme commander of the nuclear force of the DPRK, makes a decision," it added.
The threat came after Trump issued an apocalyptic warning, saying North Korea faces "fire and fury" over its missile program, after US media reported Pyongyang has successfully miniaturised a nuclear warhead.
Trump's warning followed a Washington Post report that quoted a Defense Intelligence Agency analysis as saying officials think North Korea now has "nuclear weapons for ballistic missile delivery" -- including in its intercontinental ballistic missiles.
The progress suggests North Korea is further along the path to having a deployable nuclear missile than had previously been acknowledged.
Australian prime minister Malcolm Turnbull said: “The North Korean regime's conduct is as illegal as it is reckless. It threatens the peace and stability of the region and the world, and they have to come to their senses.
“Every economic pressure that can be imposed must be imposed and Australia is playing its part. While every nation should be united in bringing this rogue regime to its senses, we note especially the importance of China's role as North Korea's major economic partner, China has unique leverage.
“And we welcome, in particular, China's support for these strong and much-more harsh sanctions imposed by the Security Council. The regime must come to its senses and stop its illegal provocations.”