The Democratic People's Republic of Korea (DPRK) warned the US on Tuesday of "merciless" attacks if it infringes on its sovereignty or dignity.
The warning comes after a US aircraft carrier strike group led by the USS Carl Vinson joined South Korean forces for exercises.
Since last year, North Korea has alarmed its neighbours with two nuclear tests and a string of missile launches.
"If they infringe on the DPRK's sovereignty and dignity even a bit, its army will launch merciless ultra-precision strikes from ground, air, sea and underwater," the North's state news agency KCNA said.
KCNA said the arrival of the US strike group was part of a "reckless scheme to attack [the] DPRK."
"On March 11 alone, many enemy carrier-based aircraft flew along a course near territorial air and waters of the DPRK to stage drills of dropping bombs and making surprise attacks on the ground targets of its army."
The USS Carl Vinson was in a regular, scheduled deployment to the region, said a US Navy spokesman.
In response to annual US-South Korea military drills, North Korea last week fired four ballistic missiles into the sea off the coast of Japan.
Last week, the US ambassador to the UN said President Donald Trump's administration was re-evaluating its North Korea strategy and "all options are on the table."