After this article was published, the Kremlin’s spokesman, Dmitri S. Peskov, issued a curt response and insisted on Wednesday that Russia’s army and people had unified around Mr. Putin.

A senior Russian general had advance knowledge of Yevgeny Prigozhin’s plans to rebel against Russia’s military leadership, according to U.S. officials briefed on American intelligence on the matter, which has prompted questions about what support the mercenary leader had inside the top ranks.

The officials said they are trying to learn if Gen. Sergei Surovikin, the former top Russian commander in Ukraine, helped plan Mr. Prigozhin’s actions last weekend, which posed the most dramatic threat to President Vladimir V. Putin in his 23 years in power.

General Surovikin is a respected military leader who helped shore up defenses across the battle lines after Ukraine’s counteroffensive last year, analysts say. He was replaced as the top commander in January but retained influence in running war operations and remains popular among the troops.

American officials also said there are signs that other Russian generals may also have supported Mr. Prigozhin’s attempt to change the leadership of the Defense Ministry by force. Current and former U.S. officials said Mr. Prigozhin would not have launched his uprising unless he believed that others in positions of power would come to his aid.

If General Surovikin was involved in last weekend’s events, it would be the latest sign of the infighting that has characterized Russia’s military leadership since the start of Mr. Putin’s war in Ukraine and could signal a wider fracture between supporters of Mr. Prigozhin and Mr. Putin’s two senior military advisers: Sergei K. Shoigu, the minister of defense, and Gen. Valery V. Gerasimov, the chief of general staff.

Mr. Putin must now decide, officials say, whether he believes that General Surovikin helped Mr. Prigozhin and how he should respond.

On Tuesday, the Russian domestic intelligence agency said that it was dropping “armed mutiny” criminal charges against Mr. Prigozhin and members of his force. But if Mr. Putin finds evidence General Surovikin more directly helped Mr. Prigozhin, he will have little choice but to remove him from his command, officials and analysts say.

Some former officials say Mr. Putin could decide to keep General Surovikin, if he concludes he had some knowledge of what Mr. Prigozhin had planned but did not aid him. For now, analysts said, Mr. Putin seems intent on pinning the mutiny solely on Mr. Prigozhin.

“Putin is reluctant to change people,” said Alexander Baunov, a senior fellow at the Carnegie Russia Eurasia Center. “But if the secret service puts files on Putin’s desk and if some files implicate Surovikin, it may change.”

Senior American officials suggest that an alliance between General Surovikin and Mr. Prigozhin could explain why Mr. Prigozhin is still alive, despite seizing a major Russian military hub and ordering an armed march on Moscow.

American officials and others interviewed for this article spoke on the condition of anonymity to discuss sensitive intelligence. They emphasized that much of what the United States and its allies know is preliminary. U.S. officials have avoided discussing the rebellion publicly, out of fear of feeding Mr. Putin’s narrative that the unrest was orchestrated by the West.

Still, American officials have an interest in pushing out information that undermines the standing of General Surovikin, whom they view as more competent and more ruthless than other members of the command. His removal would undoubtedly benefit Ukraine, whose Western-backed troops are pushing a new counteroffensive that is meant to try to win back territory seized by Moscow.

The Russian Embassy did not respond to a request for comment.

General Surovikin spoke out against the rebellion as it became public on Friday, in a video that urged Russian troops in Ukraine to maintain their positions and not join the uprising.

“I urge you to stop,” General Surovikin said in a message posted on Telegram. “The enemy is just waiting for the internal political situation to worsen in our country.”

But one former official called that message akin to “a hostage video.” General Surovikin’s body language suggested he was uncomfortable denouncing a former ally, one who shared his view of the Russian military leadership, the former official said.

There were other signs of divided loyalties in the top ranks. Another Russian general — Lt. Gen. Vladimir Alekseyev — made his own video appeal, calling any actions against the Russian state a “stab in the back of the country and president.” But hours later, he surfaced in another video, chatting with Mr. Prigozhin in the Russian city of Rostov-on-Don, where Wagner fighters seized military facilities.

“There were just too many weird things that happened that, in my mind, suggest there was collusion that we have not figured out yet,” Michael McFaul, a former U.S. ambassador to Russia, said in a phone interview.

“Think of how easy it was to take Rostov,” Mr. McFaul said. “There are armed guards everywhere in Russia, and suddenly, there’s no one around to do anything?”

Independent experts and U.S. and allied officials said that Mr. Prigozhin seemed to believe that large parts of Russia’s army would rally to his side as his convoy moved on Moscow.

Mr. Prigozhin had worked with General Surovikin during Russia’s military intervention in Syria, and had described him as the most capable commander in the Russian army. Former officials said General Surovikin did not support pushing Mr. Putin from power but appears to have agreed with Mr. Prigozhin that Mr. Shoigu and General Gerasimov needed to be relieved of duty.

“Surovikin is a decorated general with a complex history,” said Dara Massicot, a senior policy researcher at the RAND Corporation. “He is said to be respected by the soldiers and viewed as competent.”

General Surovikin and Mr. Prigozhin have both brushed up against Mr. Shoigu and General Gerasimov over tactics used in Ukraine. While the Russian military’s overall performance in the war has been widely derided as underwhelming, analysts have credited General Surovikin and Mr. Prigozhin for Russia’s few successes.

In General Surovikin’s case, that limited success was the professionally managed withdrawal of Russian troops from Kherson, where they were nearly encircled last fall and cut off from supplies. Based on communications intercepts, U.S. officials concluded that a frustrated General Surovikin represented a hard-line faction of generals intent on using the toughest tactics against Ukrainians.

Similarly, Mr. Prigozhin’s Wagner mercenaries achieved some success in taking the eastern city of Bakhmut after a nine-month slog in which, by Mr. Prigozhin’s own count, some 20,000 Wagner troops were killed. U.S. officials and military analysts say tens of thousands of troops died in the fight for Bakhmut, among them Wagner soldiers who were former convicts with little training before they were sent to war. Mr. Prigozhin frequently complained that senior Russian defense and military officials were not supplying his troops with enough weapons.

Russia’s entire military campaign in Ukraine has been characterized by a musical chairs of changing generals. Last fall, when General Surovikin was put in charge of the Russian Army’s effort in Ukraine, he was the second man to get the job, replacing a general who had lasted barely a month. General Surovikin did not last much longer, but performed far better during his weeks at the helm.

Nevertheless, by January, General Surovikin was demoted, and Mr. Putin handed direct command of the war to General Gerasimov, who promised to put Russian forces back on the offensive. General Surovikin’s demotion, military and Russia analysts say, was widely viewed as a blow to Mr. Prigozhin.