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 US and carried out by far its most powerful nuclear explosion to date, and Pyongyang says it needs its arsenal to protect itself against a US invasion.
The Biden administration has repeatedly stated that it has no hostile intent towards the North, but Kim told the "Self-Defence 2021" exhibition: "I am very curious if there are people or countries who believe that."
"There is no basis in their actions for believing that it is not hostile," he added, according to KCNA.
Kim's address came after the North in recent weeks tested a long-range cruise missile and what it said was a hypersonic weapon.
In 2018, Kim became the first North Korean leader ever to meet a sitting US president at the 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.
Washington and Seoul are security allies and Washington stations around 28,500 troops in the South 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 invasion.
The South has been stepping up its own military capabilities, successfully testing its first submarine-launched ballistic missile in September and revealed a supersonic cruise missile.
Kim accused the South of hypocrisy, saying their "unrestricted and dangerous attempts to strengthen military power are destroying the military balance on the Korean peninsula and increasing military instability and danger".
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