WASHINGTON — Attorney General William P. Barr has told Justice Department officials that he is skeptical of a conclusion by the department’s inspector general that the F.B.I. had sufficient information to open the investigation into whether any Trump associates conspired with Russia during the 2016 presidential race, according to two people familiar with the conversations.

Should Mr. Barr rebut the inspector general’s assessment, due out next week in a highly anticipated report, Mr. Trump’s allies will most likely use that pushback to dismiss the work itself. The review is expected to contradict some of the unfounded theories about the 2016 election that the president and his allies have promoted.

Mr. Barr’s doubts are significant because they could be perceived as the nation’s top law enforcement officer siding with Mr. Trump, who has long cast doubt on the legitimacy of the Russia investigation, over law enforcement officials.

His views are sure to inflame critics of Mr. Barr, who have accused him of siding with the president over the rule of law in his handling of the special counsel’s findings and in a recent speech in which he defended Mr. Trump’s use of executive authority. While it is a part of the executive branch, the Justice Department has typically sought to maintain some independence from the White House to guarantee that justice is applied fairly and not wielded as a political cudgel.