CFR, North Korea: The Nuclear Threat

I found this good question and answer piece published by the Council on Foreign Relations.
<http://www.cfr.org/pub8079/mary_crane/north_korea_the_nuclear_threat.php>

It gives a brief account of the supposed current state of the North Korean nuclear arsenal, and the U.S. administration's refusal to engage in direct negotiations with the DPRK, as doing so would be engaging in "nuclear blackmail"