An intelligence assessment drafted by the CIA months prior to the March 2003 US invasion of Iraq asserting that Saddam Hussein harbored an active weapons of mass destruction (WMDs) cache has been thoroughly debunked time and again.

But even after the deaths of more than 4,000 US soldiers and hundreds of thousands of Iraqi civilians, CIA officials have never publicly taken responsibility for getting the pre-war intelligence so wrong.

Former CIA deputy director Michael Morell, however, now owns up to the disastrous "mistakes" the agency made on the Iraqi WMD failures.

The veteran intelligence official has written The Great War of Our Time: The CIA's Fight against Terrorism from al Qa'ida to ISIS, which offers a behind-the-scenes look at numerous national security crises since 9/11. Morell writes in the book about the CIA's Iraq intelligence failures, and he apologizes to former Secretary of State Colin Powell, who told the United Nations Security Council on February 5, 2003 that Iraq had "biological weapons and the capability to rapidly produce more, many more." When WMDs weren't located in Iraq after the US invasion, Powell's credibility was destroyed.

"Let me tell you why I [apologized to] Colin Powell," Morell told VICE News before a recent appearance at the Richard Nixon Library to promote his book. "Here's a guy who had a stellar reputation… and quite frankly that reputation was tarnished when he went before the UN and laid out the case. That case turns out to be wrong. Almost every part of it turns out to be wrong. I knew he had said to folks over the years, 'You know, nobody from the agency has ever apologized to me.' And so that's why I wanted to apologize to him…. The apology applies to every single American."

Morell was somewhat defensive when asked to discuss why CIA analysts were unable to determine that Iraq had abandoned its weapons program in the 1990s. He compared the analysts to "weather forecasters."

"This is a very difficult business," he said. "I don't know a harder job in the world than trying to get an understanding of what's the status of the Iran nuclear program. Or, what's the status of North Korea's long-range missile system. Or, where does Chinese military modernization stand. Or, what are the plans, intentions, and capabilities of al Qaeda in Yemen."

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Watch the VICE News interview with Michael Morell

Ultimately, Morell said the main reason "we were not able to come up with the right answer is that we didn't do our fundamental job of penetrating [Saddam Hussein's] inner circle with a human asset. So there was no information to give to the analyst to say, 'Here's what this guy is up to.' This was our failure, and quite frankly a national security failure, to get inside of Saddam's inner circle to tell us exactly what he was up to with regards to weapons of mass destruction."

While Morell leaves no doubt that the CIA failed on Iraq, he mounts a full-throated defense when discussing the agency's so-called enhanced interrogation program, which he "doesn't like calling torture, because to call it torture says my guys were torturers, and they were told that they weren't."

"I have no doubt after spending months looking at this that [the program] was effective," Morell said. "I've seen the intelligence that these guys provided before enhanced interrogation techniques. It was not full answers to questions, it was not specific information, it was not actionable. After enhanced interrogation techniques, full answers to questions, specific information, actionable information. There's no doubt in my mind it was effective."

His analysis is at odds with the damning findings of the Senate Intelligence Committee, which last December released a declassified executive summary of its mammoth report on the CIA's torture program, an investigation that took five years to complete, cost $40 million, and led to chilled relations between the CIA and the committee.

In fact, the harshest critique in Morell's book is aimed directly at Democrats on the Senate Intelligence Committee, including the panel's former chairwoman, Dianne Feinstein, who led the oversight effort into the detention and interrogation program and said what committee staffers discovered in millions of pages of CIA documents clearly rose to the level of torture. He declined to respond to some of the more brutal findings in the Senate report, such as subjecting a handful of detainees to "rectal feeding" and whether that amounted to torture.

So how did the Senate get it wrong if it perused the CIA's own highly classified documents to reach its conclusions?

"One of the things I learned as an intelligence analyst very early on is it's very dangerous to speculate," Morell said. "When you speculate, you get things wrong a lot more then you get right. But I'll speculate for you with that caveat. Senator Feinstein made it very clear to everyone who would talk to her about this, that she wanted the report to be the nail in the coffin of the country ever doing anything like this again. Well, when you're on her staff and you hear that day after day after day, and your job is to put this report together, it takes you in a certain direction."

"Republican leaders in the House and the Senate [approved] this program back in 2002, 2003, 2004. And not only approved the program but encouraged us to go further — they thought we were risk-averse when we stopped the program for a period of time…. So what's the only way that the [Senate] can get themselves out of this discussion? To say that the CIA lied to them at the time about what we were doing and about the effectiveness of the program. That's the only way to get themselves off the hook. I can't prove any of that. I'm speculating."

VICE News tried numerous times to obtain a comment from Feinstein, but her office failed to respond to our queries.

However, a day before Morell's book went on sale, Feinstein took the unprecedented step of issuing a press release attacking Morell's contradictory claims about the torture program and said he did not even bother to read the full 6,700-page report. Feinstein's office then issued a 54-page point-by-point rebuttal to all of the assertions Morell made in his book about the efficacy of the program.

Morell, who now works for a private security firm founded by former aides to Hillary Clinton, told VICE News that the US is engaged in an "intelligence war."

"In this new era of terrorism, the enemy is very hard to find, but very easy to kill," he said. "The finding, which is the hard part, is all about intelligence. So this is an intelligence war…. You cannot capture and kill your way out of this. The other problem that you have to deal with is how do you stop the creation of new terrorists? How do you deal with the radicalization problem of young men and young women around the globe? That's something that we have not done well as a country or as a coalition of countries… and it's not going to go away until we get our arms around that."

An earlier version of this report incorrectly said the CIA's pre-war Iraq intelligence concluded that Saddam Hussein colluded with Al Qaeda. The story has been updated.