North Korea has announced it will test one of its nuclear warheads, the BBC reports. North Korea's foreign ministry declared: "[North Korea] will in the future conduct a nuclear test under the condition where safety is firmly guaranteed."

It added provocatively: "The US daily increasing threat of a nuclear war and its vicious sanctions and pressure have caused a grave situation on the Korean Peninsula."

The ministry said North Korea "can no longer remain an on-looker to the developments" - a reference to "vicious" US sanctions which have caused a situation where "the US moves to isolate and stifle" the country.

The Pyongyang regime is under considerable US-led pressure to cease and desist its nuclear weapons programme. In 1994, it signed an agreement to "freeze all nuclear-related activities", but in December 2002 restarted its Yongbyon reactor and booted two UN nuclear monitors out of the country.

A fully-operational Yongbyon reactor could, the BBC notes, "produce enough plutonium to build approximately one weapon per year". Google Earth features a nice view of the Yongbyon facility, as seen here:

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