The "wrong judgment and acts" of the US meant instability could not be resolved, he said in an address to the "Self-Defence 2021" display, according to the official Korean Central News Agency.

Pyongyang is under multiple international sanctions over its banned nuclear weapons and ballistic missile programmes, which have made rapid progress under Kim.

In 2017, it tested missiles that can reach the whole of the continental United States and carried out its most powerful nuclear explosion to date. Pyongyang says it needs its arsenal to protect itself against a US invasion.

Analysts say North Korea is seeking to normalise its status as a nuclear power.

The Biden administration has repeatedly stated that it has no hostile intent towards Pyongyang, but Kim said: "Its behaviours provide us with no reason why we should believe in them.

"I wonder if there is any person or state who believes in its claim," he added according to KCNA, "and, if any, I am curious to know who they are."

But he insisted that North Korea's weapons were for self-defence and not aimed at any particular country.

Pictures carried by state media showed Kim at the exhibition in front of the gigantic intercontinental ballistic missile (ICBM) revealed at a night-time military parade last year.

He was also shown sitting smoking with senior officials and officers, with huge photo portraits of the leader in military uniform hung in the exhibition hall.

His address came after North Korea in recent weeks tested a long-range cruise missile, a train-launched weapon, and what it said was a hypersonic warhead.

In 2018, Kim became the first North Korean leader ever to meet a sitting US president at a headline-grabbing Singapore summit.

But the talks process has been largely at a standstill since a second meeting in Hanoi the following year collapsed over sanctions relief and what Pyongyang would be willing to give up in return.

The Biden administration has said it is willing to meet North Korean officials at any time or place, without preconditions, in its efforts to seek denuclearisation.

Kim's comments and the show itself were intended to justify Pyongyang's nuclear and missile programmes as "part of its right to self-defence", said Park Won-gon, professor of North Korean studies at Ewha Womans University.

"North Korea held the exhibition on purpose to claim that their weapons development programmes are no different from those of other countries," he told AFP.

- Party time -

Washington and Seoul are security allies and the United States stations around 28,500 troops in South Korea to defend it against its neighbour, which invaded in 1950.

The South and the United States held joint military exercises in August. The wargames always infuriate Pyongyang, which decries them as preparations for an invasion.

Seoul is itself on a multi-billion-dollar drive to step up its military capabilities, successfully testing its first submarine-launched ballistic missile in September -- putting South Korea among an elite group of nations with proven SLBM technology -- and revealing a supersonic cruise missile.

Last week, Pyongyang and Seoul reconnected their cross-border hotline in a sign of thawing ties, with only a few months left in office for South Korea's pro-engagement President Moon Jae-in.

But Kim accused Seoul of "avaricious ambition" and a "double-dealing, illogical and brigandish" attitude.

Their "unlimited, dangerous attempts to strengthen military capability are breaking the military equilibrium in the region of the Korean peninsula and aggravating the military instability and danger there", he added.

The exhibition is part of the commemorations for the anniversary of the foundation of the ruling Workers' Party, and included aerobatics flights and martial arts displays.