US intelligence agencies badly misjudged al-Qaeda's ability to take advantage of political turmoil in the Middle East and regain strength across the region after Osama bin Laden was killed, according to a new book by the CIA's former deputy director.

Senior US intelligence officials have previously acknowledged failures to anticipate the Arab Spring movement, which toppled governments in the Middle East and North Africa. But the former official, Michael Morell, wrote that the CIA compounded those errors with optimistic assessments that the upheaval would eventually 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," Morell wrote in the book, a copy of which was obtained ahead of its release later this month.

Instead, "the Arab Spring was a boon to Islamic extremists across both the Middle East and North Africa," he said.

"From a counterterrorism perspective, the Arab Spring had turned to winter."

The acknowledgment represents one of the most bleak assessments of the CIA's performance during that period by an official who was in the agency's leadership at the time.

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 Egypt, Libya, Syria, Iraq and Yemen.

US officials have said recently that they expect conflicts exploited by extremists to persist for a decade or more. 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.

Morell's book, , defends the CIA's controversial use of brutal interrogation measures on terrorism suspects.

The book includes an apology to former Secretary of State Colin Powell for the CIA's erroneous prewar assessments of Iraq's weapons programmes.

But it accuses then-Vice President Dick Cheney of pressuring agency analysts to find links between Iraq and al-Qaeda that did not exist.

This article appeared in the South China Morning Post print edition as: CIA failed to see al-Qaeda's rebound

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