"If you want to talk to Kim Jong Un about his nuclear weapons you need experienced diplomats," Clinton was quoted as telling Dutch tabloid Algemeen Dagblad in an interview published Saturday.
"These are people familiar with the dossiers and who know the North Koreans and their language," Trump's presidential rival said in an interview conducted in Amsterdam and published in Dutch.
The former secretary of state said however that the US State Department was "being eroded" and that experienced diplomats on the North Korean issue were in short supply, with many having left.
"You cannot have diplomacy without diplomats," she said, adding "the danger is not being recognised by the Trump government."
"It's a real opportunity... I worry about the President's unpreparedness and lack of discipline. But I commend him for his very bold move in accepting the invitation," Richardson told AFP on Friday.
"But this is not 'The Apprentice' or a reality TV event. It's a negotiation with an unpredictable leader who has at least 20 nuclear weapons and who threatens the United States," he said.
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