Attorney General William Barr expects special counsel Robert Mueller’s report to be released in mid-April, "if not sooner," and estimates the report is nearly 400 pages long.

The new details about the highly anticipated report came Friday in a letter Barr sent to the leaders of the House and Senate Judiciary committees.

“Everyone will soon be able to read it on their own,” the attorney general said in his letter. “I do not believe it would be in the public’s interest for me to attempt to summarize the full report or to release it in serial or piecemeal fashion.”

Barr received the report from Mueller on his investigation into whether members of the Trump campaign colluded with Russia on Friday. He then sent lawmakers a four-page letter Sunday summarizing Mueller’s conclusions.

The attorney general’s new letter to Sen. Lindsey Graham, R-S.C., and Rep. Jerry Nadler, D-N.Y., provides more information regarding what details of Mueller’s report will be redacted and kept out of the public’s view. Mueller is assisting the agency in this process, Barr said.

[READ: AG Barr's letter to leaders of the House and Senate Judiciary committees]

Barr identified four categories of information that will not be made public, including material related to grand jury proceedings which by law cannot be made public, information deemed by the intelligence community to compromise sensitive sources and methods, details that could affect other ongoing investigations — including those referred by the special counsel’s office to other offices — and material that would “unduly infringe on the personal privacy and reputational interests of peripheral third parties.”

The president could also assert executive privilege to withhold certain information such as his communications with others. But Barr said the Justice Department does not intend to give the report to the White House first.

“Although the president would have the right to assert privilege over certain parts of the report, he has stated publicly that he intends to defer to me and, accordingly, there are no plans to submit the report to the White House for a privilege review,” Barr told lawmakers.

The attorney general also volunteered to testify publicly after Mueller’s report is released to the public and said he is available to appear before the Senate Judiciary Committee on May 1 and the House Judiciary Committee on May 2.

The special counsel’s 22-month probe concluded Friday when Mueller delivered his confidential report to Barr.

In his summary of Mueller’s “principal conclusions,” which was sent to Congress on Sunday, Barr said the investigation “did not find that the Trump campaign or anyone associated with it conspired or coordinated with Russia in its efforts to influence the 2016 U.S. presidential election."

The attorney general also told lawmakers he and Deputy Attorney General Rod Rosenstein concluded the evidence from Mueller’s probe “is not sufficient to establish that the president committed an obstruction-of-justice offense.”

[Opinion: Releasing the Mueller report won't change anyone's mind]