Any nuclear war, even if it involves a limited exchange of, say, 10 warheads on both sides, would be a terrible thing. But it would be much, much worse if the number of mushroom clouds on the horizon was in triple digits.

U.S. intelligence analysts say North Korea, the most unpredictably aggressive nuclear power on the planet, could have as many as 100 atomic bombs in its arsenal by 2020.

By then, Pyongyang also may have reliable, accurate missiles capable of dropping those warheads throughout Asia – and possibly as far away as the United States.

What makes those predictions especially worrisome is that North Korea’s leaders seem to be engaged right now in testing the resolve of other powers, including the United States, to stop the buildup. That can be concluded from the regime’s activities during recent months, which include testing new missiles and claiming to have detonated a hydrogen bomb.

Then, on Tuesday, U.S. Director of National Intelligence James Clapper told the Senate Armed Services Committee that North Korea has restarted a plutonium reactor that had been shut down since 2007. The reactor can make material for nuclear weapons.

Nothing the United States, the United Nations or anyone else has done to deter North Korea from building a truly fearsome arsenal, capable of killing millions of people, has worked. That country’s leaders count on fear of a war with them to deter more effective action.

But the longer it is delayed, the more reason there is to worry about war with North Korea. Clearly, in Washington and at the U.N., the situation needs to be viewed as a crisis.