North Korea has denounced as "an unacceptable provocation" military exercises scheduled between the US and South Korea.

Pyongyang has said the annual Ulchi Focus Lens drill set to be held later this month was a preparation for invasion and the move could affect its deal to dismantle its nuclear programme.

US and South Korean officials have repeatedly said the manoeuvres are "purely defensive".

The exercise will involve about 10,000 US troops based in South Korea and abroad, and a "small number" of personnel in Seoul, according to the US military.

'Extreme confrontation'

US forces said North Korea has been notified about the exercise plan set to run between 20 and 31 August.

The Committee for Peaceful Reunification of the Fatherland said the drill, staged since 1975, aimed to use force to stifle North Korea.

The drill was "an unacceptable provocation that drives the Korean peninsula situation to the phase of an extreme confrontation", it said in a statement carried by the official Korean Central News Agency.

North Korea said the exercise "poses obstacles to efforts to resolve" the standoff over its nuclear programmes and hinders reconciliation between the two Koreas.

"It remains our position that we respond with good faith to good faith and with merciless punishment to provocation," the committee said.

'War deterrent'

"Our army and the people will further solidify our war deterrent."

The North's reference to its "deterrent" is usually its nuclear programmes.

Last month Pyongyang shut down its sole functioning nuclear reactor in Yongbyon in return for energy aid under a deal with the US, China, Japan, South Korea and Russia.

The February deal also calls for it to disclose all nuclear programmes and disable its facilities.

About 28,000 US troops are stationed in South Korea as a legacy of the 1950-53 Korean War which ended in a cease-fire, leaving the two Koreas still technically at war.