Washington (CNN) Attorney General William Barr 's review of the origins of the 2016 Russia investigation and surveillance issues surrounding President Donald Trump's campaign will be "broad in scope and multifaceted," examining actions by US and foreign intelligence agencies, "as well as non-governmental organizations and individuals."

This latest description of Barr's controversial project was in a letter from the Justice Department to House Judiciary Chairman Jerry Nadler, marking the first time the department had explained in detail the information being gathered from the intelligence community since Trump granted Barr broad authority to declassify sensitive intelligence materials late last month.

Monday's letter was released publicly just as the committee began a separate hearing on "lessons" learned from special counsel Robert Mueller's report on the Russia probe.

The focus on foreign intelligence has already had some key allies wary of being dragged into what some see as a political probe, as CNN previously reported , and the letter notes that Barr will work closely with the intelligence community regarding declassification of any relevant information.

"It is of great importance to the Department to protect classified information by preventing the unwarranted disclosure of sensitive sources, methods, and techniques and materials where such disclosure would endanger the personal safety of US government employees or friendly foreign partners, harm US national security interests, or compromise the ability of US government agencies," wrote assistant Attorney General Stephen Boyd.

Monday's letter also came as a deal was struck between the Justice Department and Democrats on Capitol Hill who've threatened to hold Barr in contempt over Mueller-related materials and have been critical of the attorney general's remarks about intelligence agencies "spying" on the Trump campaign. Nadler said Monday that the Justice Department will begin providing Congress with some documents from the Mueller report related to obstruction of justice, putting off a looming court showdown.

For months, Trump and his GOP allies had demanded the Justice Department formally examine the genesis of the FBI's counterintelligence investigation into the Trump campaign, and CNN reported in May that Barr had tapped US Attorney John Durham, a career federal prosecutor in Connecticut, to lead the effort.

The review will seek "to determine whether the investigation complied with applicable policies and laws," Boyd said Monday.

"The Attorney General looks forward to obtaining a better understand of the critical period leading up to the 2016 presidential election, which to date has not fully been examined," Boyd added. "As the U.S. approaches another election season, it would be most prudent to timely draw upon the lessons learned from our recent history."

While not specifying in Monday's letter, Barr has previously signaled that his review will include an examination of ex-British intelligence officer Christopher Steele's work compiling research about Trump and Russia in a dossier that was commissioned by Fusion GPS, a research and investigative firm.

Steele's role also is under scrutiny by the Justice Department's inspector general, who is looking at the surveillance of Trump's former foreign policy adviser Carter Page after he left the campaign. The review includes how the FBI and the Justice Department used the information from the dossier to obtain a court order to monitor Page under the Foreign Intelligence Surveillance Act and in subsequent FISA renewal applications.