"I should say that we have enough nuclear bombs to defend against a US attack," the North Korean official told ABC News when asked how many nuclear bombs it possessed.
Asked whether Pyongyang was building more nuclear bombs, Kim said: "Yes."
His open admission about North Korea's nuclear weapon ambitions further clouds efforts to bring a diplomatic resolution to the nuclear crisis gripping the Korean peninsula.
Washington believes North Korea possesses one or two crude bombs and may have reprocessed enough plutonium for half-a-dozen more, from spent fuel rods at its Yongbyon nuclear complex.
The Stalinist state also has an arsenal of missiles. It fired a long-range missile over Japan and into the Pacific Ocean in 1998.
Six party talks
Kim, North Korea's chief negotiator in six-party talks designed to wean the communist state from its nuclear weapons programme, would neither confirm or deny that North Korea had a missile capable of hitting the mainland US.
He was also noncommital when asked about North Korea's ability to put a nuclear warhead on its long-range missiles.
"I want you to know that our scientists have the knowledge, comparable to other scientists around the world," he said. "You can take it as you like."
"I should say that we have enough nuclear bombs to defend against a US attack"
Kim Gye Gwan,
North Korea Vice Foreign Minister
But Kim stressed that North Korea doesn't "have any intention at all of attacking the US".
The State Department had no comment about the report.
President George Bush said in an interview with Fox News on Wednesday that international sanctions against North Korea remained an option.
"North Korea must understand ... that the United States is serious about working with four other countries to convince them to get rid of their weapons systems," he said.
Pyongyang has boasted publicly in the past of possessing a nuclear deterrent and has vowed never to dismantle its atomic arsenal unless the United States drops its "hostile" policy.
In February, it declared that it had developed nuclear weapons to protect itself against a US attack and would indefinitely boycott multilateral talks aimed at dismantling its atomic programmes.
North Korea had attended three round of six-party talks with the United States, China, Japan, South Korea and Russia but refused to attend the fourth round scheduled in September last year, citing what it termed hostile US policy.
"North Korea must understand ... that the United States is serious about working with four other countries to convince them to get rid of their weapons systems"
US President George Bush
The official Korean Central News Agency, Pyongyang's mouthpiece, said on Wednesday that new talks would take place only when the United States agrees to its demands.
"As for the resumption of the six-party talks, it entirely depends on the US response to the DPRK's (North Korea's) call for creating conditions and an environment for their resumption," a North Korean foreign ministry spokesman was quoted as saying.
The statement, which followed a rare meeting between US and North Korean officials in New York on Monday, punctured hopes raised by China for an early resumption of talks.
Beijing's ambassador to the United Nations, Wang Guangya, had indicated that North Korea had decided to attend a new round of talks soon, possibly within "the next few weeks".
Pyongyang's latest verbal attack came just days after senior US and North Korean diplomats met on Monday for the second time in less than a month in New York.
The US State Department said North Korea had said at the meeting that it would return to the talks, although no date was mentioned.
On Wednesday, State Department spokesman Sean McCormack said the administration has "not heard confirmation from any source that North Korea has agreed to any date or timeframe for the resumption of six-party talks".
He added that no specific arrangements have been made at this point for the next round.
But the Pyongyang Foreign Ministry spokesman on Wednesday complained of receiving mixed signals from Washington.