This would be the first time that Kim has been quoted directly about the miniaturized warheads, even though North Korean state media has reported their existence before.
"The nuclear warheads have been standardized to be fit for ballistic missiles by miniaturizing them," state media agency KCNA quoted Kim as saying as he inspected a nuclear facility, Fox News reported.
"This can be called true nuclear deterrent," he added.
The latest developments from the country come amid heightened tensions following claims it tested a hydrogen bomb in January.
On Monday at State of Air Force briefing at Pentagon, the Air Force's top officer Gen. Mark Welsh told Fox News, that while the actions of North Korea are "very worrisome," the country does not have the capability to put a nuclear warhead on top of a missile and shoot it at the United States.
North Korea warned Monday of pre-emptive nuclear strikes after the United States and South Korea began holding their biggest ever war games.
Tensions remain high after North Korea's recent nuclear test and rocket launch, which prompted the United Nations to adopt tough new sanctions.