Rick, you make a keen comparison between North Korea and Iran.

Events of last week offered a chilling hypothetical. Last Friday, news broke that a South Korean naval ship sank near the border uneasily shared with North Korea. Immediately, speculation arose that Pyongyang had intentionally attacked the vessel.

This would be less than surprising, considering that within the last year, among other acts of intransigence and aggression, North Korea has conducted nuclear tests, repeatedly threatened attacks against South Korea and the U.S., and captured South Korean fishermen who had crossed into disputed waters. Yet South Korea has since determined that North Korean involvement in the vessel’s sinking is unlikely.

But suppose for a moment that Pyongyang really had attacked. As a former editor of mine pointed out in a conversation over the weekend, the reaction of the international community would have been limited. Precisely because North Korea possesses nuclear arms, South Korea and the world would have been forced to tread cautiously.

It’s also worth noting that six-party talks — a.k.a. engagement — did not prevent Pyongyang from acquiring nuclear weapons.

In July 2006, just as North Korea was testing its rocket-delivery system, I was traveling in South Korea and Japan, two member-countries of the six-party talks. I remember the uneasiness and frustration expressed by several journalists there as the rocket launched. It was odd and frightening to think that, beyond my sight, a rocket was whizzing past, and with it, the international balance was shifting. By October 2006, just three months later, it was too late for the world to do much. North Korea had become the world’s eighth atomic power.

Since then, North Korea has been a constant problem. It has been hard enough to get Pyongyang to merely participate in six-party talks — much less make substantive concessions. In May 2009, the DPRK went so far as to call talks with the United States “meaningless.” Nuclear-weapon status has only emboldened Kim Jong-il and his followers. They are an armed agent of instability in Asia.

The Obama administration should consider the North Korean precedent as it determines how to deal with Iran. One thing is certain: the United States’s problem-solving flexibility will only decrease as Iran approaches nuclear-power status.