North Korea says its seriously considering a plan to fire nuclear-capable missiles at Guam, according to state-run media.
A spokesman for North Korea's military told KCNA that it would carry out a pre-emptive operation if there were signs of US provocation.
The warning comes after President Donald Trump warned North Korea it would be met with "fire and fury" if it continued to threaten the US in a marked escalation of rhetoric.
The statement from North Korea mentioned using the Hwasong-12, the intermediate range missile tested in May. North Korea said at the time the missile can carry a heavy nuclear warhead, and independent analysis seems to fit with their statement.
The US military keeps a continuous presence of nuclear-capable bombers in Guam, which would make it an attractive target for a nuclear strike. North Korea specifically mentioned these bombers "which get on the nerves of DPRK and threaten and blackmail it through their frequent visits to the sky above Korea."
CNN's Jim Sciutto says that the US flew two B1-B bombers over Korean Peninsula Mon out of Anderson AFB in Guam, part of "continuous bomber presence."
But the US maintains a Terminal High-Altitude Area Defense missile interceptor in Guam specifically made to protect from medium-range missiles. THAAD has performed well in test conditions but never intercepted a shot fired in anger.
Earlier, Pyongyang said it was ready to give Washington a "severe lesson" with its strategic nuclear force in response to any US military action.