American intelligence agencies have noticed signs some time ago that Yevgeny Prigozhin, the head of the Russian mercenary group Wagner, had the intention of going against the Russian leadership from the middle of June, the American daily Washington Post reported.
Another American newspaper, the New York Times, said that the information was both solid and alarming.
Late on Friday, Prigozhin's forces left their camps in Ukraine and crossed into Russia, taking control of the southern city of Rostov-on-Don, and then headed for Moscow.
Suddenly, the advance was suspended on Saturday afternoon, and Russian media said Wagner's troops would return to Ukraine, while Prigozhin would flee to neighboring Belarus.
The Kremlin has said it will not prosecute Prigozhin or Wagner's gunmen.
The Times has said that as US intelligence officials have discovered that Prigozhin has been preparing for military action, they have expressed concern about the chaos that could occur in Russia, a state with a powerful nuclear arsenal.
US agencies believe Russian President Vladimir Putin was tipped off at least a day in advance that Prigozhin - once his close ally - was organizing the rebellion.