While I think US diplomacy on North Korea for decades has left much to be desired -- it basically amounts to maintaining a strong front and begging China to do something -- I give the Bush administration a lot of credit for sticking to its demand on six party talks.
The trouble caused by North Korea in the region is hardly a bilateral issue with the US. Each of its neighbors is affected in some way by its reckless international behavior, its economic decrepitude, and its horrifying abuse of its own citizens. Accordingly, a bilateral agreement alone woudl not solve the North Korean question, and, if anything, it would drive a wedge between the US and Japan, which would have serious consequences for the region. The Bush administration learned from 1994 that the US cannot reach a separate deal with Pyongyang and dictate it to Japan after the fact, without Japan fearing abandonment (one of the classic poles of alliance politics -- accordingly, in 1994 there was a lot of talk in Japanese security policy circles asking how Japan can ensure its own defense in the face of a potentially unreliable US).
In any event, the bargaining environment is most likely irrelevant, because I don't think it's possible for negotiations to persuade a country that has worked hard to develop nuclear weapons to give them up. The solution to the North Korean question depends on, as always, Beijing, and to a lesser extent Seoul.