North Korea says it is considering missile strikes near the US territory of Guam, just hours after US President Donald Trump threatened Pyongyang with "fire and fury".
North Korea's official news agency said it was mulling a plan to fire medium-to-long-range rockets around Guam, where US strategic bombers are based.
The statement marks a sharp rise in rhetoric between the two countries.
The UN recently approved further economic sanctions against the country.
Mr Trump's comments followed a media report that claimed North Korea had made a nuclear warhead small enough to fit inside its missiles.
The Washington Post report, which cited US intelligence officials, suggested North Korea was developing nuclear weapons capable of hitting the US at a much faster rate than expected.
The Korean Central News Agency (KCNA) said its military was "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".
It said the plan would be reported to the Supreme Command after "full examination and completion" and put into practice at the order of its leader Kim Jong-un, South Korean news agency Yonhap reported.
In another statement citing a different military spokesman, North Korea also accused the United States 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 United States should stop its "reckless military provocation" against North Korea to avoid any military action, the army spokesman said.
The heated rhetoric between the US and North Korea intensified after Pyongyang tested two intercontinental ballistic missiles in July, claiming it now had the ability to hit the US.
Mr Trump told reporters on Tuesday (Wednesday NZT): "North Korea best not make any more threats to the US. They will be met with fire and fury like the world has never seen."
Veteran US Republican Senator John McCain was sceptical about Mr Trump's statement.
"The great leaders that I have seen they don't threaten unless they are ready to act and I'm not sure that President Trump is ready to act," Mr McCain said.
NZ Prime Minister Bill English said he was worried comments from Mr Trump could inflame the situation with North Korea.
Mr English said the comments were unhelpful in an environment which was very tense.
"Everyone wants to avoid military confrontation, and the path ahead there is for North Korea to comply with UN sanctions and for international pressure to push them in that direction."
Mr English said he would raise his concerns with the United States if the country continued to issue similar statements.
- BBC / Reuters