WASHINGTON — The former C.I.A. director John O. Brennan overrode the recommendation of two senior officers in early 2017 to side with lower-level analysts and affirm the agency had high confidence in one of its major judgments in the assessment of Russia’s 2016 election interference: that President Vladimir V. Putin of Russia tried to help Donald J. Trump by discrediting Hillary Clinton.
The revelation by Mr. Brennan in his new book, “Undaunted,” will probably fuel additional Republican criticism of the intelligence agencies’ findings. But Mr. Brennan defended his actions, saying he was affirming the determinations of the analysts steeped most deeply in the intelligence, not intervening for political reasons.
“I didn’t change a single analytic judgment in that intelligence community assessment,” Mr. Brennan said in an interview that is set to be broadcast on C-SPAN’s “Book TV” in the coming days.
The declassified assessment, released in January 2017 during the closing days of the Obama administration, said that while the C.I.A. and F.B.I. had high confidence in the finding about Mr. Putin, the National Security Agency had moderate confidence, a lower level.
Mr. Brennan said the National Security Agency originally had high confidence in the conclusion but that Adm. Michael S. Rogers, its director at the time, reduced the confidence level. Mr. Brennan said Admiral Rogers had concerns about the confidence level but did not explain them. Admiral Rogers, now retired, has declined to discuss the deliberations.
While the finding about Mr. Putin’s efforts to help Mr. Trump’s election chances has been affirmed by a bipartisan Senate report and by the former C.I.A. director Mike Pompeo, now the secretary of state, President Trump’s allies disparage it and have sought to undermine it by pointing to the agencies’ differing confidence levels. John Ratcliffe, the director of national intelligence who was previously one of Mr. Trump’s staunchest supporters in Congress, has said that Mr. Putin was merely trying to undermine American democracy and sow chaos, rather than supporting Mr. Trump’s election.
All three agencies had high confidence in the conclusion that Mr. Putin developed a clear preference for Mr. Trump.
In addition to writing about the debate over the confidence level of the other finding in his book, scheduled to be released next week, Mr. Brennan has also answered questions about the intelligence assessment posed by John H. Durham, the U.S. attorney assigned by the Justice Department to review the intelligence agencies’ examination of the Russian interference campaign in 2016.
Mr. Brennan said that after the agency’s Russia analysts made their initial draft assessment, two more senior officers in the mission center that oversaw intelligence on Russia expressed concerns to him. The two officers, one an analyst and the other with a background in operations, suggested the confidence level be reduced to moderate.
“They came up and talked to me about it and I listened to them because I wanted to make sure I understood exactly what their concerns were,” Mr. Brennan said in the C-SPAN interview. “And I encouraged them to talk to the authors of the assessment and determine if the judgment should stay at high confidence or medium confidence.”
Intelligence agencies characterize their confidence in intelligence typically at three levels: low, moderate or high. High-confidence conclusions typically have multiple sources and draw from different kinds of intelligence, such as electronic intercepts, satellite photos or human sources of information. A moderate, or medium, level of confidence could reflect that the sourcing behind a conclusion could be weaker.
Mr. Brennan declined to discuss the sources behind the judgment that Mr. Putin sought to aid Mr. Trump. But other former officials have said that a C.I.A. informant, who has since been extracted from Russia, was particularly important for making the judgment; because Mr. Putin eschews electronic devices, intercepting his communications is notoriously difficult.
Mr. Brennan said he had been reviewing new intelligence about Russian interference since the summer of 2016 and was steeped in the material. In his conversation with the two senior officials, he realized they may not have seen all of the material that he and the analysts who wrote the initial conclusion had reviewed.
“In my conversation with them, it was apparent to me, and I say in the book, that they had not read all the intelligence that I had read,” Mr. Brennan said. “So my own view was to support the analysts.”
In recent months, Republicans have been stepping up attacks on how the F.B.I. and C.I.A. looked into accusations of Russian interference and contacts between Moscow and the Trump campaign. Many have been awaiting information from Mr. Durham’s inquiry.
Mr. Durham has told Mr. Brennan his is not a target of any criminal inquiry. But Mr. Durham’s interview of the former C.I.A. director could be included in a report. It is not clear when, or if, Mr. Durham will release a report.
At the same time, Mr. Ratcliffe’s office has stepped up efforts to declassify information surrounding aspects of the Russia investigation, including names of Obama administration officials who requested the identity of Americans mentioned in intelligence reports and other intelligence reports.
On Tuesday, Mr. Ratcliffe released small portions of previously classified reports in an apparent bid to help the president politically. The material was unverified and suggested that Russian intelligence had acquired information that Hillary Clinton had approved a plan for her 2016 campaign to “stir up a scandal” against Mr. Trump by tying him to the Russian hackers who had broken into Democratic servers.
One of the snippets released by Mr. Ratcliffe included a reference to handwritten notes by Mr. Brennan, who wrote that he had briefed President Barack Obama on the information about Mrs. Clinton.
Mr. Brennan sharply criticized Mr. Ratcliffe’s “disturbing release of selective information.” As C.I.A. director, he said, he briefed the White House on information about election interference regardless of what candidate the information referred to. But he cast doubt on the information, and said even if true, it would not reflect anything illegal by Mrs. Clinton.
“The accuracy of the information is very much in doubt and is questionable,” Mr. Brennan said. Mr. Ratcliffe, Mr. Brennan added, “is trying to give Trump any shiny object they can to district from problems Trump is encountering on a daily basis.”