North Korea says it will develop a plan by mid-August to launch four intermediate range missiles at Guam, hitting waters near the US territory.
State media said the plan would then be presented to North Korean leader Kim Jong Un, who would make a decision on whether to proceed.
The report cited a commander in the Korean People's Army, who said the Hwasong-12 rockets would travel above Japan and hit the sea 30-40km from Guam.
"The Hwasong-12 rockets to be launched by the KPA (Korean People's Army) will cross the sky above Shimane, Hiroshima and Koichi Prefectures of Japan," the report said, citing General Kim Rak Gyom, commander of the Strategic Force of the KPA.
"They will fly 3356.7km for 1065 seconds and hit the waters 30 to 40 kilometres away from Guam."
The report added that US President Donald Trump's "fire and fury" comments earlier this week were a "load of nonsense", saying only "absolute force can work on him".
Guam governor reassured of US protection against North Korea
Meanwhile, Guam governor Eddie Calvo said the United States has reassured him of its protection in the event of a North Korean missile attack.
In a special address yesterday, Mr Calvo called for calm, saying he had been in touch with the White House.
"An attack or threat on Guam is an attack or threat on the United States. They have said that Americans will be defended."
And he called for calm in the country.
"I want to reassure the people of Guam, and currently there is no threat to our island or the Marianas. There is no change in the threat level resulting from North Korea events."
Dededo mayor Melissa Savares said people on the island had put their faith in God and the US military to protect them from any missile attacks from North Korea.
She said while the threat was worrying, people on the island continued to go about their daily lives.
"We have the THAAD missile defence, we have the Anderson Airforce Base. From what we hear in the community we trust in defence system that we have.
"We have a beautiful island, we still have tourists that come. We pray a lot here in Guam, our faith is evidence that we believe that God will take care of us."
Auckland University professor Stephen Hoadley said Guam authorities were not worried because experts were sceptical about North Korea's claimed missile capability.
"There is a lot of debate whether these North Korean missiles, firstly, are accurate and, secondly, can survive the re-entry from space into the earth's atmosphere with the risk of burning up - can the North Koreans actually put a nuclear warhead onto these missile?"
Retired US army General Wesley Clark said of Mr Trump's latest comments that it was absurd to engage in schoolboy rhetoric with North Korea.
"We have a very strong military, the emphasis should be on deterrents.
"War could start from an accidental miscalculation on the Korean peninsula, and it's more likely with that escalatory rhetoric from the president of the United States, I'm sorry to say."
The New Zealand Defence Force has confirmed an air force aircraft was in Guam as part of a military exercise, but would not comment on the North Korean threat against the country.