Mr. Trump’s remark was the starkest example of a recent pattern in Washington, Mr. White said.

Too often, he said, the United States has declared it would use force to stop something from happening — such as China’s expansion in the South China Sea, and during President Barack Obama’s administration, Syria’s use of chemical weapons — and has failed to do so. “Trump’s antics amplify that message tenfold,” Mr. White said.

The official Chinese reaction to Mr. Trump’s comments was mild. The Foreign Ministry reiterated standard points about the North Korea dispute: that it should be resolved with diplomacy and that all parties should avoid escalating the situation.

In part, the modesty of that response was due to the fact that Chinese leaders are currently more focused on domestic politics than foreign policy, analysts said.

President Xi Jinping and other senior officials are attending an annual retreat at Beidaihe, a beach resort east of Beijing, where the political machinations are more intense this year than usual. Mr. Xi is assumed to be finalizing the new lineup of China’s top leaders for the next five years, expected to be announced at a national congress that could be convened as soon as next month.

There may also be a scheduling reason for the mildness of China’s response. Mr. Trump’s daughter Ivanka and her husband, the White House adviser Jared Kushner, are scheduled to visit China next month with their children. Mr. Kushner is a primary White House contact for China, and Beijing is putting considerable effort into ensuring that the visit goes smoothly. The visit is also seen as a planning operation for Mr. Trump’s own trip to China in November.

Images of Mr. Kushner, his wife and their children at a family dinner with Mr. Xi at his Beijing estate, Zhongnanhai, would fit well into Mr. Xi’s playbook of appearing to have “the world in its proper orbit, around him,” said Douglas Paal, vice president of the Carnegie Endowment for International Peace.