North Korea's envoy in Britain says Pyongyang has a nuclear deterrent that is ready to use and powerful enough to deter any US attack.
Ambassador Mr Ri Yong Ho told Reuters in an interview on Thursday that the communist state, which is in dispute with Washington over its nuclear intentions, would only use its capability in self-defence.
North Korea has long hinted it had a nuclear bomb. It said last month it was prepared to demonstrate the existence of its nuclear deterrent "when an appropriate time comes".
But Thursday's comments appear to be the first time it has explicitly stated that it has a nuclear weapon ready to deploy.
Mr Ri said the deterrent was made of plutonium, most of which was recently reprocessed but was extracted before a 1994 freeze on its nuclear weapons programme under a pact with Washington. He said the deterrent was ready to use immediately.
Asked if North Korea would only use it in self-defence, he added: "Of course. Self-defence is a right of any nation, only in self-defence."
In an apparent bid to defuse the nuclear crisis, Washington last month offered Pyongyang unspecified security assurances for the first time, in exchange for a complete, verifiable and irreversible end to its suspected weapons programme.
Washington has ruled out a formal non-aggression treaty.