He further unsettled South Korean officials by declaring in May, during an interview with Reuters, that he would be willing to negotiate directly with Kim Jong-un, the North Korean leader, to try to stop the North’s nuclear arms program. “I would have no problem speaking to him,” Mr. Trump said.

At first, Mr. Trump’s remarks were largely dismissed in South Korea, but the news media here sounded a growing alarm about them as it became clearer that he would become the Republican nominee. “It is scary just to imagine Trump, who often doesn’t remember what he has said, getting elected president and manipulating Korean Peninsula issues by drastically shifting his positions,” a South Korean newspaper, Kyunghyang Shinmun, wrote in an editorial in May.

South Korean officials have told reporters that they are trying to reach out to Mr. Trump’s policy advisers in hopes of persuading him that the American military presence here benefits the United States as well as South Korea.

The Rodong Sinmun article was the second about Mr. Trump to appear in North Korea’s state news media in two days. On Tuesday, a lesser propaganda outlet, the website DPRK Today, carried what it called an opinion piece submitted by Han Young-muk, whom it identified as an ethnic Korean scholar in China. Such articles are seen as having less authority than official commentaries in Rodong Sinmun, which hew closely to the party line.