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Meanwhile, the Obama administration says the sinking of a South Korean warship, which has been blamed on Pyongyang, can not be classed as terrorism.
The US State Department said Monday the incident is not enough to put the DPRK back on a U.S. terror blacklist.
It said that the sinking of the frigate Cheonan in March was a "provocative action" and a violation of the truce that ended the Korean war. But it added that the incident was an act of one state's military against another.
Pyongyang has denied that it had any links with the incident. The DPRK has previously been on the U.S. "state sponsors of terrorism" list, but was removed from the list in 2008 following progress in the now-stalled efforts to get the country to abandon nuclear weapons.