In a more alarming development, experts at California’s Middlebury Institute of International Studies, said last week that satellite images suggested that Pyongyang could be preparing to launch a missile or space rocket.
In response to questions about what the signs of activity at rocket launch facilities meant, Mr Biegun replied: “The short answer is: we don’t know.”
He added that “the door remains open” for further negotiations. “Nothing can be agreed until everything’s agreed,” he said.
Nuclear and North Korea analysts expressed scepticism about his statements.
“Biegun: “Nothing can be agreed until everything can be agreed.” – a losing strategy,” tweeted Jenny Town, a Korea specialist at the Stimson Centre, a Washington think tank.
Others commented that the insistence on full denuclearisation before the lifting of any sanctions would create a bottleneck with Pyongyang, which has consistently argued for reciprocal concessions.
“If we don’t move off this position, we have nowhere to go,” Vipin Narang, a MIT nuclear expert, told Vox. “There’s no zone of agreement if we insist on everything — I mean everything, complete surrender — up front.”