Advisers who have spoken recently with Trump about the Russia investigation said the president was sharply critical of Attorney General Jeff Sessions, as well as Deputy Attorney General Rod J. Rosenstein, who oversees the Mueller operation — but did not broach the idea of firing Mueller.

“I think he realizes that would be a step too far,” said one adviser, who spoke on the condition of anonymity to share a private conversation.

Rather, Trump appeared to be contemplating changes in the Justice Department’s leadership. In recent discussions, two advisers said, Trump has called the attorney general “weak,” and complained that Rosenstein has shown insufficient accountability on the special counsel’s work. A senior official said Trump mocked Rosenstein’s recent testimony on Capitol Hill, saying he looked weak and unable to answer questions. Trump has ranted about Rosenstein as “a Democrat,” one of these advisers said, and characterized him as a threat to his presidency.