Analysts say definitions and a plan of action are needed to ensure the talks lead to progress.
Others who know about them are reluctant to say so, for fear of the police.
Some say trust must be earned, but others suggest a treaty could ease Kim’s mind over ending his weapons program.
Official media say nuclear production facilities and test sites are being closed, however.
The plant could not likely obtain material necessary for its operations under sanctions supported by China, a source says.
North Korean media meanwhile highlight joint performances calling for 'unification' of the Korean peninsula.
Busloads of workers are seen going into China, with fewer seen making the return trip.
The vehicle, a military jeep, was being moved with the help of one Chinese unit, but was seized by another on the Yalu River.