If North Korea launches missiles on Guam, it would take only about 14 minutes for the rockets to reach the US territory, the island's Homeland Security spokeswoman announced.
Jenna Gaminde told a press briefing on Thursday that the residents would be immediately notified by the 15 All-Hazards Alert Warning System sirens, located in low-lying areas throughout the island, the Pacific Daily News reported.
Gaminde's remarks comes after North Korea announced earlier on Thursday that the nation has a detailed plan for a missile strike near Guam, where about 7,000 US troops are stationed, using four intermediate-range ballistic rockets.
The plan calls for sending 12 rockets over Japan to crash in the waters about 30 miles from Guam, which is 2,100 miles east of the Korean peninsula.
"Our office will be notified from the military and will utilize all forms of mass communication to get the message out to the public.
"Local media, village mayors and social media would be used to disseminate information.
"If you hear the sirens, tune into local media - radio, print, television - for further instructions," the spokeswoman added.