The pledge came at a Monday meeting overseen by leader Kim Jong Un and follows last week's staging of joint air drills by South Korea and the United States.

The agenda was topped by "the issue of constantly expanding and intensifying the operation and combat drills of the (Korean People's Army) ... strictly perfecting the preparedness for war", the official Korean Central News Agency said.

The meeting of North Korea's central military commission comes as commercial satellite imagery suggests "extensive parade preparations" are underway in Pyongyang ahead of key state holidays this month.

North Korea celebrates the founding anniversary of its armed forces on Wednesday and the "Day of the Shining Star" on February 16. The latter is the birthday of Kim Jong Il, son of North Korea's founder Kim Il Sung and father of Kim Jong Un.

South Korea's Joint Chiefs of Staff said Tuesday it was closely monitoring areas surrounding Pyongyang's parade training ground, adding it had seen a "great increase in personnel and vehicles" in recent days.

- North Korean balloon -

Seoul and Washington have moved to bolster joint military drills following a year of sanctions-busting weapons tests by North Korea, infuriating Pyongyang, which sees such joint exercises as rehearsals for invasion.

Last week, the security allies staged joint air drills featuring strategic bombers and stealth fighters, prompting Pyongyang to warn such exercises could "ignite an all-out showdown".

The joint exercises, their first this year, came a day after US Defense Secretary Lloyd Austin and his South Korean counterpart vowed to boost security cooperation to counter an increasingly belligerent nuclear-armed North.

North Korea's foreign minister has said the move to ramp up joint drills crossed "an extreme red line".

On Monday, Seoul's defence ministry said a North Korean balloon had crossed over to its airspace at the weekend, but concluded it did not pose a threat.

It was believed to be a weather balloon, Yonhap News agency reported, citing officials, and the ministry said it had taken "measures" without elaborating.

The report came after Washington shot down a suspected Chinese surveillance balloon, with Beijing saying that it was a civilian airship that had accidentally crossed into US airspace.

- Beef up military -

Experts say Monday's meeting of North Korea's top brass aimed to highlight the country's readiness to face down upcoming joint military drills between South Korea and the United States -- and also stress it was prepared for an actual war.

"North Korea is hinting about the possibility of military action in the future in the name of operational and combat training and war preparedness," said Hong Min, researcher at the Korea Institute for National Unification.

Yang Moo-jin, professor at the University of North Korean Studies in Seoul, added that the meeting signalled Pyongyang's determination to "aggressively beef up its military".

Kim recently called for an "exponential" increase in Pyongyang's nuclear arsenal, including mass-producing tactical nuclear weapons and developing new missiles for nuclear counterstrikes.

Kim has also said his country must "overwhelmingly beef up military muscle" in 2023 in response to what Pyongyang calls US and South Korean hostility.