Washington (CNN) Attorney General William Barr "disagrees" with a forthcoming report by the Justice Department's inspector general that says the FBI had enough information in 2016 to launch an investigation into President Donald Trump's campaign, The Washington Post reported Monday.

The Post, citing conversations with people familiar with the matter, said Barr has also privately told associates that he thinks other federal agencies, "such as the CIA, may hold significant information that could alter (inspector general Michael) Horowitz's conclusion on that point."

Horowitz is due to release his report next week on the FBI probe, which has caused "disagreement" at the department because of his "central conclusions" of the nearly two-year-long Russia investigation, according to the Post. Trump and many conservatives have long accused the FBI of wrongdoing in its investigation into connections between Russian election meddling and the Trump campaign, and Barr has previously criticized the handling of the probe.

It's unclear how Barr will make his concerns with the report known, the paper said, noting that either he or a senior official at the department could submit a letter to be included in the report. Although the attorney general could opt out of including a letter with the report, he could instead make his objections public, the Post said.

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