The Wall Street Journal's Seoul bureau chief said South Koreans are used to aggression from the North but are "uncertain" about the future now that that rhetoric has escalated.
Jonathen Cheng said the war of words between Kim Jong Un and President Trump are a "cause for concern."
But, he added that China's announcement it will stay neutral unless Trump strikes first is "some relief" for the locals.
"People are definitely concerned to a new level here," he said.
Cheng said that in the past, the White House's statements have been lukewarm and "predictable," but Trump's aggressive stance is a change to that status quo.
He said that new South Korean President Moon Jae In is also in a sticky situation because of how he ran on a message of diplomacy with Pyongyang.
Cheng said that Moon has unsuccessfully sought several meetings with Kim and is "between a rock and a hard place" with the North ramping up its threats against the South's top ally.
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