“The Chinese don’t like North Korea’s nuclear program, but the current situation does serve their longer-term interests in eroding American leadership, because it provides a whole new set of circumstances in which America shows its weakness,” said Hugh White, a former senior defense strategist in the Australian government.
Mr. Trump’s threat has particularly unsettled America’s main Asian allies, Japan and South Korea, adversaries and neighbors of North Korea that have increasingly vocal lobbies for acquiring their own nuclear weapons to counter Pyongyang’s.
China and Japan are far from being close. But China is trying to improve its relations with South Korea, and it sees opportunity there as Mr. Trump threatens pre-emptive action against North Korea, which would be anathema to the liberal government of the South’s new president, Moon Jae-in.
Attempts by Secretary of State Rex W. Tillerson and Defense Secretary Jim Mattis to calibrate Mr. Trump’s comments did not alleviate the credibility problem that China hopes to exploit, analysts said.
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.
For China, North Korea is not the only vexing United States-China issue on which the Trump administration’s credibility has recently faltered. Last week, China appears to have narrowly escaped punishing American trade tariffs.
The White House was reported to be considering an investigation of alleged Chinese violations of American intellectual property, which could have led to steep tariffs on Chinese imports. But the plan appears to have been pulled because the administration needed China’s support last weekend for stiff new United Nations sanctions against North Korea.
“The Chinese figure the vaunted 301 measures are on hold until after the Trump family trips to Beijing,” Mr. Paal said, referring to the section of the 1974 Trade Act that the administration was planning to use to punish China.
Over all, the Chinese leadership — which is accustomed to belligerence from North Korea, its estranged ally — does not believe Mr. Trump would actually carry out his threat to strike North Korea, said Yun Sun, a senior associate at the East Asia program at the Stimson Center.
China has listened to three generations of bluster from the rulers of North Korea, including the current leader, Kim Jong-un, so grandiose and alarmist language is nothing new to them, she said. It is common for North Korea to talk about “turning Seoul into a sea of fire and a pile of ashes,” she noted, referring to the capital of South Korea.
And while North Korea and the United States are hardly equals, China is likely to similarly dismiss Mr. Trump’s “rhetorical war” against the North, Ms. Sun said.
“A striking impression is how little China sees the threats by either North Korea or Trump as credible,” she said, adding, “I don’t think the Chinese are losing sleep today.”
Outwardly, at least, Chinese leaders appear to be reacting calmly to Mr. Trump’s words because they understand that they need not be taken seriously, said Mr. White, the former defense strategist for Australia. That in itself is a major problem for the United States, especially as it competes with China for influence in Asia, he said.
“Trump is making empty threats to North Korea,” Mr. White said. “It is credible to say that America will attack North Korea if North Korea actually attacks the U.S. or allies — as Mattis has done. But it is not credible to threaten to attack if North Korea keeps issuing verbal threats towards America.”
Would China benefit if Mr. Trump actually started a war with North Korea? “If the U.S. gets a swift and decisive win, then that’s a big loss for China,” Mr. White said.
“But if, as is much more likely, it turns into a costly disaster for the United States, South Korea and Japan, in the end that might well mark the end of the United States’ leadership in Asia,” he said.