Several experts said North Korea’s warning was probably a bump in the road rather than a dire threat to next month’s meeting. But they said it pointed up the complexity of the negotiations that Mr. Trump faces.
“It lays down a probable marker that exercises will be on the table in negotiations,” said Victor D. Cha, a Korea scholar at Georgetown University whom the Trump administration had considered as ambassador to Seoul.
Joel S. Wit, a senior fellow at the Johns Hopkins School of Advanced International Studies who negotiated with North Korea during the Clinton administration, said Mr. Kim was pulling a page from Mr. Trump’s playbook.
“It’s probably them acting like North Koreans after being pussy cats since January,” he said. “Acting like tough guys. Like Trump saying he would walk out of the summit if he didn’t like the deal.”
Christopher R. Hill, who negotiated with North Korea during the George W. Bush administration, said it was possible that the threat was more serious. The North, he noted, has a history of insulting the South, and normally, the United States comes to the defense of its ally.
Mr. Trump did not immediately react to Mr. Kim’s warning, and the White House issued only a bland statement. “We are aware of the South Korean media report,” the press secretary, Sarah Huckabee Sanders, said. “The United States will look at what North Korea has said independently, and continue to coordinate closely with our allies.”
While Mr. Trump has raised expectations for a breakthrough with Mr. Kim, other officials have tried to strike a more cautious note. In an interview on the CBS program “Face the Nation” last Sunday, Secretary of State Mike Pompeo, who has met Mr. Kim twice, said, “We have our eyes wide open with respect to the fact that the North Koreans have not proved worthy of their promises, but we’re hopeful that this will be different.”