NORTH Korea's favoured method of diplomacy is blackmail; it has threatened the mass starvation of its own populace if its enemies did not provide food, and now it has returned to its old habits of nuclear brinkmanship. With a regime as unstable as that of Kim Jong II, yesterday's threats to reverse an agreement about safe disposal of nuclear material cannot be ignored. By announcing that it would reactivate nuclear materials that it had agreed to store, North Korea has reminded the region that its least tractable problem has not gone away. By now at least, no-one expects the malevolently eccentric regime in Pyongyang to stick by its agreements. It signed one of these in 1994; to cease its dubiously peaceful nuclear activities in return for a jointly supervised power generating capacity and supplies of oil from South Koreans and the US. These supplies, North Korea now argues, have not been

provided to its satisfaction. Like his father Kim II Sung, the ''Dear Leader'' is playing on fears of what a desperate and isolated regime might do with the products of its own aged nuclear infrastructure.

As always, the problem for North Korea's neighbours and the US, is how to manage a regime in terminal decline. Even without the nuclear card, the consequences of a sudden and complete collapse could be disastrous; civil war and a tide of starving refugees creating a humanitarian disaster to equal any this century. Despite behaviour well-exemplified by this latest gamble, the region has had no option but to bend to the bluster of what the US has designated a ''terrorist regime''. In the past, those opposed to this bizarre dictatorship have had to observe powerlessly the grievous sufferings of a populace stuffed with propaganda but starved essentials. The failure of North Korea to take seriously peace talks with the South earlier this year, and now with this threat to renege on a painfully-won nuclear agreement suggests that it may be time that the waiting game was replaced with a more proactive

approach.