Senior US intelligence officials have previously acknowledged failures to anticipate the 2011 Arab Spring movement, which toppled governments in the Middle East and North Africa.
But the former CIA deputy director Michael Morell writes that the spy agency compounded those errors with optimistic assessments that the upheaval would prove devastating to al- Qaeda.
"We thought and told policy-makers that this outburst of popular revolt would damage al-Qaeda by undermining the group's narrative," The Washington Post quoted Morell as writing in his upcoming book.
The acknowledgment represents one of the most bleak assessments of the CIA's performance during that tumultuous period by an official who was in the agency's leadership ranks at the time, the Post commented.
Four years after the initial street protests in Tunisia that set off the Arab Spring, al-Qaeda and its progeny have gained territory and strength in countries such as Egypt, Libya, Syria, Iraq and Yemen.
The CIA declined to comment on the criticism in Morell's book, but US officials stressed that events turned rapidly to al-Qaeda's advantage largely because the political movements that seemed promising at first have largely failed to lead to effective new governments.
It includes an apology to former secretary of state Colin Powell for the CIA's erroneous prewar assessments of Iraq's weapons programmes but accuses then-Vice President Cheney of pressuring agency analysts to find links between Iraq and al- Qaeda that did not exist.
The book's most sobering passages are devoted to al- Qaeda's resurgence after the death of bin Laden, which had raised hopes among US counterterrorism officials that the organisation was on a path to defeat.
"We were lax in creating our own windows into what was happening, and the leadership we were relying on was isolated and unaware of the tidal wave that was about to hit," he says. As those governments fell, so did their ability to contain militant groups inspired by al-Qaeda, Morell writes.
