China’s Defense Minister Is Under Investigation, U.S. Officials Say

China’s defense minister, Gen. Li Shangfu, has been placed under investigation, according to two U.S. officials, fueling speculation about further upheaval in the military after the abrupt removal of two top commanders in charge of the country’s nuclear force.

General Li has not been seen in public in more than two weeks. He had been expected to take part in a meeting last week in Vietnam, but there was no word of his attendance. Asked by reporters on Friday about General Li’s whereabouts, Mao Ning, a spokeswoman for the Chinese Foreign Ministry, said she had no information.

The investigation points to questions about the Communist Party’s leader Xi Jinping’s confidence in his own military, a pillar of his ambitions abroad and dominance at home.

Just six weeks ago, Mr. Xi replaced the two most senior commanders of the People’s Liberation Army Rocket Force, which oversees China’s nuclear missiles. The abrupt dismissals suggested that Mr. Xi was seeking to reassert his control over the military and purge perceived corruption, disloyalty and dysfunction from its ranks, analysts have said.

Many experts believe that the military commanders may be accused of corruption, though some have said that suspicions of disloyalty toward Mr. Xi within the People’s Liberation Army, or P.L.A., may be involved. In July, China also dismissed the foreign minister, Qin Gang — another official who had risen rapidly under Mr. Xi — without explanation. The two U.S. officials, who spoke on the condition of anonymity, said they believed General Li had been placed under investigation on suspicion of corruption.

Mr. Xi still appears politically unassailable, with the Communist Party leadership, military top brass and security services packed with his loyalists. Even so, the sudden downfall of such high-ranking officials has exposed the pitfalls in a system so dominated by a single leader and has raised questions about Mr. Xi’s judgment because the officials under scrutiny been promoted by him.

Su Tzu-yun, an expert on the People’s Liberation Army at the Institute for National Defense and Security Research, a think tank in Taipei that is funded by the Taiwanese government, said he was more than 90 percent sure that General Li had been removed from his post.

“For Xi Jinping, this is a loss of face, and in the Chinese military and across China, people will notice, even if they don’t say so openly,” Mr. Su said. “It’s not going to force him from power, but it will erode his prestige as ruler.”

General Li, 65, was promoted to minister of national defense in March, after late last year joining the Central Military Commission, the council led by Mr. Xi through which the party controls the military.

General Li’s last public appearance was in late August, when he spoke at a forum in Beijing attended by officials from African countries. It is not unusual for People’s Liberation Army commanders to be away from the public spotlight, though as the military’s chief diplomat, the defense minister’s absences are more noticeable.

The Reuters news agency reported on Friday, citing anonymous sources, that General Li did not attend the scheduled talks last week with Vietnamese officials — an unusual absence that suggested something might be amiss.

Officers may be “turning in their colleagues in exchange for leniency, or else cadres are preemptively attacking rivals,” said Drew Thompson, a former U.S. defense official who has long studied China’s military and is now a fellow at the Lee Kuan Yew School of Public Policy in Singapore. “Ideology and loyalty is the core issue, but anti-corruption is the tool used to achieve the end state of Xi and the party’s political security.”

For much of his career, General Li was deeply involved in developing and acquiring the People’s Liberation Army’s growing array of rockets, missiles and other advanced weapons. He appeared to have Mr. Xi’s trust as a weapons expert who, like Mr. Xi, was the son of a veteran in Mao Zedong’s revolutionary forces.

An engineer by training, General Li accumulated a sparkling résumé in rocketry, weapons development and the manned space program. He was appointed the inaugural deputy commander of the Strategic Support Force, which Mr. Xi created in late 2015 as part of a sweeping reorganization of the Chinese military. The Strategic Support Force brings together China’s efforts in new realms of military rivalry, like space, cyberoperations and espionage, advanced communications, and psychological warfare.

In 2017, General Li was appointed the director of the Chinese military’s Equipment Development Department, and it was his role there that made him a target of U.S. government sanctions in the next year. Citing his role in acquiring Russian fighter planes and surface-to-air missiles, Washington barred General Li from, among other things, obtaining a U.S. visa.

China has rebuffed invitations from the United States for talks between General Li and the defense secretary, Lloyd J. Austin III, saying that the Biden administration should first lift the sanctions.

“As the lyrics of a well-known Chinese song goes, when friends visit, bring out the fine wine. When jackals and wolves visit, bring out the shotgun,” General Li said at an annual security meeting in Singapore this year.

The apparent official scrutiny on General Li raises questions about the fate of other senior Chinese officials, especially in the armaments and aeronautics sectors where he had risen through the ranks.

Gen. Ju Qiansheng, the commander of the People’s Liberation Army’s Strategic Support Force — where General Li previously served — has been out of public view for months, and did not attend a reception for military officers in late July, raising the possibility that he may also be part of an investigation.

“I think the cases we’ve seen now are probably just the tip of the iceberg,” said Mr. Su, the researcher in Taipei. “The armaments acquisition system of the People’s Liberation Army often deals with the market, so the proportion of technical officers that gets into trouble is quite high.”

Rahm Emanuel, the U.S. ambassador to Japan, who has been tweaking Mr. Xi on X, the social media platform formerly known as Twitter, said in an interview on Friday that the Chinese government should explain General Li’s absence and also why Mr. Xi skipped the Group of 20 summit last week in India and other commitments.

In a post on X on Friday, Mr. Emanuel asked if General Li had been placed under house arrest.

“There’s just too much,” Mr. Emanuel said. “When you know the history of China, given all the tension economically and internally, people are being arrested left and right.”

Motoko Rich, Sui-Lee Wee and Eric Schmitt contributed reporting.