North Korea, the secretive, nuclear-armed “hermit kingdom”, claimed today that it had shut down the atomic reactor in Yongbyon where it produced plutonium for use in weapons.

Although the shut-down has yet to be confirmed officially by inspectors from the International Atomic Energy Agency, the move reduces by a small notch the crisis atmosphere inflamed by Pyongyang’s atomic bomb test last October.

The move marks the first serious concession in the five-year nuclear brinkmanship of Kim Jong Il, North Korea’s enigmatic dictator.

The nuclear crisis on the Korean peninsula began in 2002 when Pyongyang ejected all IAEA inspectors. Washington’s principal negotiator at the six-party talks, Assistant Secretary of State Christopher Hill, has previously suggested that the decommissioning of Kim’s nuclear facilities could be completed by the end of the year, with further concessions delivered “within months”.

But Mr Hill, on a visit to Japan today, warned that the shut-down was “only meaningful in so far as we take additional steps.” Even as it drew back from the brink yesterday North Korea, once identified by the administration of George Bush as being one third of the “axis of evil”, was careful to allow only a tiny release of pressure on the United States.

Washington, said a Pyongyang foreign ministry spokesman, must also lift all current sanctions imposed on the communist state before North Korea takes any further steps down the path to nuclear disarmament.

Those steps, he said, would include providing “declared” details of the nuclear weapons programme and closing the facilities where bombs were made.

Before any of that happens, though, another key demand by Kim’s regime is that it be permanently struck off Washington’s list of “sponsors of terrorism”.

Although heavily conditional on future US concessions, the North’s shut-down of Yongbyon’s reactor may represent a critical milestone on the road back to the so-called “six-party talks”.

The negotiations are seen by the other participants - the United States, China, Russia, Japan and South Korea - as the only realistic chance of peacefully persuading North Korea to abandon its nuclear weapons programme. The talks, suspended since March, are scheduled to resume in Beijing this Wednesday.

By apparently closing the Yongbyon facility - a large atomic energy plant about 60 miles north of the capital - North Korea fulfilled one part of the disarmament deal to which it agreed in February. IAEA inspectors entered North Korea yesterday and were yesterday engaged in what is likely to be a two-day process of verifying the shutdown while the reactor cools down.

According to Pyongyang’s representatives at the United Nations in New York, the shutdown followed the arrival in North Korea of the 6,200 tons of fuel oil, sent from South Korea as compensation for the energy “lost” through the closure of Yongbyon. The shipment represents more than a tenth of the 50,000 tons of oil promised to the North.

Pyongyang had earlier said that it would only fulfill its side of the bargain once every ounce of oil had arrived.

Washington suspended deliveries of oil to North Korea in early 2003 when it accused Pyongyang of breaking a disarmament deal and of embarking on secret uranium enrichment.

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