An increasingly isolated North Korea said yesterday it would conduct its first-ever nuclear test, blaming a US "threat of nuclear war and sanctions" for forcing its hand.
The statement by North Korea's foreign ministry, carried on the official KCNA news agency, was condemned by neighbouring Japan as "unacceptable" and caused South Korea to increase its security alert.
Britain said it would view any nuclear test as a highly provocative act.
The announcement confirms weeks of rumours the communist state was planning a test and came amid increasingly sour relations with the outside world after it test-fired missiles in July.
"The US extreme threat of a nuclear war and sanctions and pressure compel the DPRK (North Korea) to conduct a nuclear test, an essential process for bolstering nuclear deterrent, as a corresponding measure for defence," the statement said.
But it added that North Korea would never use nuclear weapons first and would "do its utmost to realise the denuclearisation of the peninsula and give impetus to the world-wide nuclear disarmament and the ultimate elimination of nuclear weapons."
Analysts say North Korea probably has enough fissile material to make six to eight nuclear bombs but probably does not have the technology to make one small enough to mount on a missile.
Pyongyang's latest and, to date, most extreme sabre-rattling was most probably aimed at trying to force the United States into direct talks and end a painful financial crackdown on impoverished North Korean offshore bank accounts, analysts said.
Japan's new prime minister, Shinzo Abe, said any nuclear test by North Korea would be unacceptable.
"North Korea needs to realise that unless it responds to the concerns of international society, its situation will only worsen," he told reporters.
The North Korean statement comes as Mr Abe readies for talks with leaders in China and South Korea from this weekend.
Officials in China - North Korea's main suppliers of aid - gave no immediate official response to the report. Top South Korean security officials met and issued a statement outlining the increased security alert, the presidential Blue House said.