North Korea Monday hit out at the United States and South Korea over their planned joint military drill this month which it said was "an all-out war rehearsal" that could ignite conflict on the Korean Peninsula.

The allies will hold Ulchi Freedom Guardian, which is largely a computer-simulated exercise, on August 20-31 to improve their combat-readiness amid high cross-border tensions.

The US and South Korea "are going to stage again Ulchi Freedom Guardian joint military exercises for invading the DPRK from August 20 to 31 at a time when they are becoming evermore undisguised in their hostile policy and confrontation racket against it," the North's Korean Central News Agency said.

The allies describe their annual exercises as defensive and routine but the North habitually terms them a rehearsal for invasion and launches its own counter-exercises.

"The army and people of the DPRK have grown stronger in their will to take revenge on the US," Pak Rim-Su, head of the North army mission at the border village of Panmunjom, said in a protest notice over the drill to General James D. Thurman, commander of US Forces Korea, quoted by KCNA.

The Rodong Sinmun, the mouthpiece of the ruling Workers' Party, also said the exercise demonstrated Washington's hostile attitude.

"This is a vivid expression of its hostile policy toward the (North) and a dangerous act to ignite a new war on the Korean Peninsula at any cost," said the commentary carried by KCNA, quoted by South Korea's Yonhap news agency.

"The joint military exercises are an all-out war rehearsal against the (North) from the viewpoint of military hardware and scale of forces to be involved in them and their program and nature," it said.

The drill will involve many of the 28,500 US troops stationed in the South as well as some 3,000 from abroad but there will be no field training, the US military has said.

In addition to the regular annual exercises, South Korea has staged a series of drills alone or with US troops since it accused the North of torpedoing one of its warships with the loss of 46 lives in March 2010.

The North denied the charge but went on to shell a border island in November 2010, killing four South Koreans.

Tensions are high after the North's failed rocket launch in April, seen by the United States and its allies as an attempted ballistic missile test.

Pyongyang has also threatened attacks on the South's government and conservative media for perceived insults to its regime.