Mr. davies said the u. s.believes pyongyang may have already developed uranium-enrichment facilities beyond the one site it showed a visiting american scientist , siegried hecker , last month .
Mr. hecker didn 't respond to several messages left at his office and home .
赫克没有回复记者发往他办公室和住所的多条留言。
Siegfried hecker , a co-director of stanford university 's centre for international security and cooperation who has made several visits to north korea 's nuclear facilities , said the nuclear test appeared to be aimed at fixing problems pyongyang 's technicians encountered in their first test in october 2006 .
Siegfried hecker , a us nuclear scientist who has visited north korea 's atomic facilities repeatedly , says it probably needs to make one more atomic test in addition to those conducted in 2006 and 2009 to be able to miniaturise a warhead for deployment on a missile .
The u. s. dispatched mr. bosworth in the aftermath of a new report by stanford scientist siegfried hecker over the weekend revealing the north 's new uranium-enrichment capabilities following a trip to pyongyang .
