The Defense Intelligence Agency—in A Primer on the Future Threat, The Decades Ahead: 1999-2020 (SECRET/NO FORN) from July 1999—concludes North Korea’s nuclear weapons will weigh no less than 650-750 kg:
In the near term, it is unlikely that the North Korean nuclear weapons program can achieve nuclear yield from a 100 kg device. An early-generation warhead weighing 650-750 kg is the best Pyongyang could achieve.
Such a warhead would, presumably, require a test. The CIA concluded tests are unnecessary for simple fission devices.
Lieutenant General Patrick M. Hughes, (USA-Ret.) authored the report while Director of DIA from 1996-1999.
FAIR’s Seth Ackerman notes Hughes was “widely believed” to be a key source of classified material leaked to the Washington Times’ Bill Gertz and Rowan Scarborough.
Excerpts from the report—including this one—were published in Scarborough’s Rumsfeld’s War. I may post a .pdf of the document if I have time later this week.